What does Mark 13:23 mean?

This is the overall theme of Mark chapter 13. Hard things will happen. False teachers with supernatural powers will convince people they are Jesus returned. Wars (Mark 13:7), natural disasters (Mark 13:8), persecution (Mark 13:9), and betrayal (Mark 13:12) will decimate the human population and nearly destroy the earth. We must remember that Jesus warned us, and these are things we should expect.

Jesus explains that just as we can tell the changing of the seasons from the growth cycle of a tree, we should remember His words and be prepared (Mark 13:28–31). James 1:5 promises that if we lack wisdom, we only need to pray. We start with the Bible (2 Timothy 3:16–17) and rely on the Holy Spirit, the Spirit of truth (John 14:16–17). Obedience is integral to the process; if we trust and love Jesus, we will obey Him (John 14:15).

No one knows when the end times will come (Acts 1:6–7). The beginning—the rapture—is imminent, which means nothing needs to happen before Jesus comes to take His followers from the earth. It is the height of foolishness, then, to claim that numerology or ancient pagan mythology or even new revelation will reveal the date to us. It is also foolishness to declare that wars or natural disasters mean the end is near when Jesus specifically states that "these are but the beginning of the birth pains" (Mark 13:8).

We are to be alert (Mark 13:35) but not obsess about dates. We are to spread the gospel (Matthew 28:19–20), not hide from the dangers of the world. And we are to read the Bible so we know the truth and aren't deceived by false teachers. If we do this, we can be sure that we are prepared.