What does Matthew 25:39 mean?

At some point in the end times (Matthew 24:3), Jesus divides a large group of people into two groups. He welcomed the first group into His kingdom, saying they had cared for Him when He was most in need (Matthew 25:35–36). These people are connected to God's predestination (Matthew 24:34), a theme associated with those who come to saving faith in Christ (Ephesians 4:1; Matthew 24:22; Mark 13:27; Romans 11:7; Titus 1:1). This contrast is especially clear when Jesus turns to condemn the other group (Matthew 25:41).

This group described as righteous (Matthew 25:37) has no memory of ever helping Jesus, Himself, in person. Given that this judgment occurs in the end of days, most or all the people present will never have seen Jesus in the flesh until this very moment. So, they are responding to His approval by repeating it in the form of a question. When, and how, did they serve to meet the needs of Christ?

The King gives them a powerful and profound answer in the following verse. Those who love other believers (1 John 3:11) and serve them (John 13:31–35) prove by their actions that they are true followers of Christ (John 14:15). When God's people care for each other (Matthew 10:40–42), it is as if they are caring for Jesus, Himself (Matthew 25:40).