In Luke 12:45-46, Jesus tells a story of a man who says "My Master is delaying his coming," and Jesus responds by saying He will "appoint him a portion with the unbelievers." Can you clarify this? It sounds as if Jesus is saying that a believer can lose salvation.
One could take this verse and misinterpret it to think that a person can lose their salvation. Fortunately, Scripture does not teach this, so we need to take a closer look at the passage to understand it properly.
First, what do we know of the slave in the parable in vs. 45-46. Since the slave refers to Jesus as “Master," it implies the slave is a believer, but in the parables (and in Scripture generally) we often see unbelievers pictured as slaves to God alongside believers. For example, God called all of Israel His servants (see Leviticus 25:55, Deuteronomy 32:36, 43), yet clearly, not all of Israel were believers (Hebrews 3:19). This simply shows how God rules over unbelieving people the same as believers, and He can use all men to His glory.
Consider the case of Pharaoh, when God delivers the Israelites from Egypt. In Exodus 14:18, God says, “Then the Egyptians will know that I am the LORD, when I am honored through Pharaoh, through his chariots and his horsemen.” Romans 9:17 is similar, “For the Scripture says to Pharaoh, “FOR THIS VERY PURPOSE I RAISED YOU UP, TO DEMONSTRATE MY POWER IN YOU, AND THAT MY NAME MIGHT BE PROCLAIMED THROUGHOUT THE WHOLE EARTH.” Obviously, Pharaoh was not a believer.
Returning to the context of this particular parable in Luke, Jesus had just finished severely rebuking the Pharisees and scribes. The Pharisees, who were the religious leaders of Israel, were in charge of God’s servants at this time. Although they were in charge, they clearly were not giving the Israelites] "their rations at the proper time," just as we read in the parable. Therefore, the Pharisees were not doing as their Master had commanded, and Jesus was rebuking the Pharisees through this parable. It's important to note that Scripture refers to all of Israel as God’s servants, which would include the unbelieving Pharisees. Therefore, this is another example of unbelievers who were called God’s servants.
In the verses you mentioned, Jesus is specifically talking about the future event of His second coming. In that moment, He is referring to those who God will appoint as stewards over His servants. This refers to the apostles, in particular, but also to all church leaders and teacher who are commissioned to feed God’s sheep. Just as Jesus told Peter three times to “feed My sheep” (John 21:15-17), pastors are told to feed God’s sheep (1 Peter 5:2).
Just as all of Israel are God’s servants, likewise all men (and particularly all who seek to lead God's people) can be called God’s servants, both believers and unbelievers. Those who are true believers will obey and will feed God’s sheep, and they will be doing His will. Those who are false teachers will not obey, but instead they will mistreat the flock. Jesus warns us of these false teachers (e.g., Matthew 7:15-23, 2 Peter 2:1-3).
Note that these false teachers know the Master’s will, but, just like the Pharisees, because they are not true believers, they do not follow His will. As a result, they are assigned a place with the unbelievers. The main point here is that those slaves referred to in vs. 45 and 46 are not believers, and, therefore they are not "losing their salvation" as they were never saved.
It may seem strange that there would be those who call themselves Christians, both pastors and laymen, who ultimately never accepted Christ themselves, but Scripture warns us that this will happen. In perhaps one of the most ominous passages of Scripture, Jesus tells us of those who thought they followed Him while on Earth will be shocked at the judgment to learn otherwise. He tells them, “I never knew you.” (Matthew 7:21-23) 1John 2 speaks of anti-Christs, and verse 19 says, “They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, so that it would be shown that they all are not of us.”
Scripture gives us the assurance that these "servants" were no servants at all, as they were truly unbelievers. As a result, the passage in Luke 12 does not teach that true believers can lose salvation.