Bible Answer

What caused Old Testament believers to do anything righteous or pleasing to God?

After Old Testament believers were given the gift of faith, the Holy Spirit didn’t permanently stay to guide them, so how were they able to hold onto that faith, much less serve God?

First, the Holy Spirit has always been required to bring a person to saving faith and also to glorify God, whether before or after Christ's death and resurrection. It was this way for the believing in Israel:

IS. 44:2  Thus says the LORD who made you
And formed you from the womb, who will help you,
‘Do not fear, O Jacob My servant;
And you Jeshurun whom I have chosen.
IS. 44:3 'For I will pour out water on the thirsty land 
And streams on the dry ground;
I will pour out My Spirit on your offspring
And My blessing on your descendants;
IS. 44:4 And they will spring up among the grass 
Like poplars by streams of water.’
IS. 44:5  “This one will say, ‘I am the LORD’S’; 
And that one will call on the name of Jacob; 
And another will write on his hand, ‘Belonging to the LORD,’ 

Notice the Lord promises to pour out His Spirit on future generations of Israel to bring them to the Lord in faith. This has always been the ministry of the Holy Spirit. Likewise, in the age of the church, the Spirit must draw men and women to Jesus in order to be saved, but there are differences in the Holy Spirit’s ministry to men and the manner of His operation after Pentecost.

Prior to Pentecost the Holy Spirit is shown in scripture to come “to” men or to come “upon” men. For example, Saul experienced the Spirit of the Lord coming upon him just before he entered into battle (1 Samuel 10:6). Later after Saul had disobeyed God and disqualified himself to hold the throne of Israel, the Spirit departed from Saul (1 Samuel 16:14). This pattern is repeated in other places in the Old Testament. The Spirit of the Lord will come upon men for a period of time, and at some later point the Spirit will depart when His purpose has been met.

There is much evidence in the scriptures that indicate the Holy Spirit was responsible for the regenerating work of faith and guiding the Old Testament Saints periodically: 

NUM. 27:18 So the Lord said to Moses, “Take Joshua the son of Nun, a man in whom is the Spirit, and lay your hand on him;
JUDGES 3:10 And the Spirit of the Lord came upon him, and he judged Israel. When he went to war, the Lord handed over to him Cushan-rishathaim king of Mesopotamia, so that he prevailed over Cushan-rishathaim. 
1SAM. 10:10 When they came there to the hill, behold, a group of prophets met him; and the Spirit of God rushed upon him, so that he prophesied among them.
EZEK. 11:5 Then the Spirit of the Lord fell upon me, and He said to me, “Say, ‘This is what the Lord says: “This is how you think, house of Israel, for I know your thoughts. 
EZEK. 11:19 And I will give them one heart, and put a new spirit within them. And I will remove the heart of stone from their flesh and give them a heart of flesh,
EZEK. 11:20 so that they may walk in My statutes, and keep My ordinances and do them. 
EZEK. 36:26 Moreover, I will give you a new heart and put a new spirit within you; and I will remove the heart of stone from your flesh and give you a heart of flesh.
EZEK. 36:27 And I will put My Spirit within you and bring it about that you walk in My statutes, and are careful and follow My ordinances. 

Furthermore, if we look at the Old Testament writings, we must conclude that each appointed Prophet and King who has written the scriptures, had been illuminated by the Holy Spirit, guiding them to write the words on the pages. This further confirms that the Spirit was alive and working through the Saints in the Old Testament because all scripture is God-breathed:

2TIM. 3:16 All Scripture is inspired by God and beneficial for teaching, for rebuke, for correction, for training in righteousness;
2TIM. 3:17 so that the man or woman of God may be fully capable, equipped for every good work.

Secondly, because the Spirit came upon and left these men throughout their lives we can assume that their flesh began to take over at certain points in their lives (just as it does for us today). For example, King Saul was tormented and disgraced during his reign; King David murdered and committed adultery. Additionally, we see proof in 1 Samuel of the Spirit leaving King Saul:

1SAM. 16:14 Now the Spirit of the Lord left Saul, and an evil spirit from the Lord terrified him.

The Old Testament Saints (men and women) were all considered righteous (born again) because they believed on the Promises in which God gave. Hebrews 11 shows us very distinct evidence of this truth: 

HEB. 11:1 Now faith is the certainty of things hoped for, a proof of things not seen. 
HEB. 11:2 For by it the people of old gained approval.
HEB. 11:3 By faith we understand that the world has been created by the word of God so that what is seen has not been made out of things that are visible. 
HEB. 11:4 By faith Abel offered to God a better sacrifice than Cain, through which he was attested to be righteous, God testifying about his gifts, and through faith, though he is dead, he still speaks. 
HEB. 11:5 By faith Enoch was taken up so that he would not see death; and he was not found because God took him up; for before he was taken up, he was attested to have been pleasing to God. 
HEB. 11:6 And without faith it is impossible to please Him, for the one who comes to God must believe that He exists, and that He proves to be One who rewards those who seek Him. 
HEB. 11:7 By faith Noah, being warned by God about things not yet seen, in reverence prepared an ark for the salvation of his household, by which he condemned the world, and became an heir of the righteousness which is according to faith.
HEB. 11:8 By faith Abraham, when he was called, obeyed by going out to a place which he was to receive for an inheritance; and he left, not knowing where he was going. 
HEB. 11:9 By faith he lived as a stranger in the land of promise, as in a foreign land, living in tents with Isaac and Jacob, fellow heirs of the same promise; 
HEB. 11:10 for he was looking for the city which has foundations, whose architect and builder is God.
HEB. 11:11 By faith even Sarah herself received ability to conceive, even beyond the proper time of life, since she considered Him faithful who had promised. 
HEB. 11:12 Therefore even from one man, and one who was as good as dead at that, there were born descendants who were just as the stars of heaven in number, and as the innumerable grains of sand along the seashore.
HEB. 11:13 All these died in faith, without receiving the promises, but having seen and welcomed them from a distance, and having confessed that they were strangers and exiles on the earth. 
HEB. 11:14 For those who say such things make it clear that they are seeking a country of their own. 
HEB. 11:15 And indeed if they had been thinking of that country which they left, they would have had opportunity to return. 
HEB. 11:16 But as it is, they desire a better country, that is, a heavenly one. Therefore God is not ashamed to be called their God; for He has prepared a city for them.
HEB. 11:17 By faith Abraham, when he was tested, offered up Isaac, and the one who had received the promises was offering up his only son; 
HEB. 11:18 it was he to whom it was said, “Through Isaac your descendants shall be named.” 
HEB. 11:19 He considered that God is able to raise people even from the dead, from which he also received him back as a type. 
HEB. 11:20 By faith Isaac blessed Jacob and Esau, even regarding things to come. 
HEB. 11:21 By faith Jacob, as he was dying, blessed each of the sons of Joseph, and worshiped, leaning on the top of his staff. 
HEB. 11:22 By faith Joseph, when he was dying, made mention of the exodus of the sons of Israel, and gave orders concerning his bones.
HEB. 11:23 By faith Moses, when he was born, was hidden for three months by his parents, because they saw he was a beautiful child; and they were not afraid of the king’s edict. 
HEB. 11:24 By faith Moses, when he had grown up, refused to be called the son of Pharaoh’s daughter, 
HEB. 11:25 choosing rather to endure ill-treatment with the people of God than to enjoy the temporary pleasures of sin, 
HEB. 11:26 considering the reproach of Christ greater riches than the treasures of Egypt; for he was looking to the reward. 
HEB. 11:27 By faith he left Egypt, not fearing the wrath of the king; for he persevered, as though seeing Him who is unseen. 
HEB. 11:28 By faith he kept the Passover and the sprinkling of the blood, so that the destroyer of the firstborn would not touch them. 
HEB. 11:29 By faith they passed through the Red Sea as through dry land; and the Egyptians, when they attempted it, were drowned.
HEB. 11:30 By faith the walls of Jericho fell down after the Israelites had marched around them for seven days. 
HEB. 11:31 By faith the prostitute Rahab did not perish along with those who were disobedient, after she had welcomed the spies in peace.
HEB. 11:32 And what more shall I say? For time will fail me if I tell of Gideon, Barak, Samson, Jephthah, of David and Samuel and the prophets, 
HEB. 11:33 who by faith conquered kingdoms, performed acts of righteousness, obtained promises, shut the mouths of lions, 
HEB. 11:34 quenched the power of fire, escaped the edge of the sword, from weakness were made strong, became mighty in war, put foreign armies to flight. 
HEB. 11:35 Women received back their dead by resurrection; and others were tortured, not accepting their release, so that they might obtain a better resurrection; 
HEB. 11:36 and others experienced mocking and flogging, and further, chains and imprisonment. 
HEB. 11:37 They were stoned, they were sawn in two, they were tempted, they were put to death with the sword; they went about in sheepskins, in goatskins, being destitute, afflicted, tormented 
HEB. 11:38 (people of whom the world was not worthy), wandering in deserts, on mountains, and sheltering in caves and holes in the ground.
HEB. 11:39 And all these, having gained approval through their faith, did not receive what was promised, 
HEB. 11:40 because God had provided something better for us, so that apart from us they would not be made perfect.

The Spirit of God has always worked alongside the other two Persons of the Trinity since the very beginning, the fundamental difference is that the Holy Spirit today indwells believers permanently instead of temporarily to accomplish His work. Additionally, the Spirit is also responsible for bringing conviction to believers.

We suggest doing a study on Hebrews, specifically Chapter 11, for an in-depth understanding of the Holy Spirit's role in the lives of believers in the Old Testament.