What does Mark 3:13 mean?

Jesus often finds it difficult to get away from the crowd, but this time seclusion is essential. The night before, He had spent alone praying to God (Luke 6:12). It is only after conferring with His Father that He chooses who will be His closest followers. He has already chosen Simon and Andrew (Mark 1:16–17), James and John (Mark 1:19–20), and Levi (Mark 2:13–14). Now He rounds out the number of His inner group, or as Mark calls them, "the twelve."

The "mountain" is probably one of the hills around Capernaum. The town sits at 600 feet below sea level. The land rises steeply, and within a few miles comes to 236 feet. That's not very high as far as altitude goes, but it's still a rise of over 800 feet.

When Jesus "calls" these men, from the Greek root word proskaleomai, He doesn't mean for them to just leave their jobs or their homes, which is still a significant sacrifice. Jesus commissions them to follow Him, mind and spirit. These are men who apparently show interest in His ministry beyond the healings. Their hearts are open to His teaching.

This is the same attitude we should have. When Jesus calls us to follow Him, we should respond with our whole selves: our minds, hearts, time, effort, priorities. If necessary, we should also be ready to sacrifice our relationships (Luke 14:26), possessions (Mark 10:21), reputations (Philippians 3:3–11), and even our lives (Philippians 2:17).

But here, the twelve are just beginning. They don't know that ten of them will be martyred for Jesus and an eleventh exiled. They just know that at this moment, they need to say yes. Over the coming years, they will allow Jesus to work in their hearts and learn that the sacrifice is worth it (1 Corinthians 2:9). God promises He can do that in us, as well (Philippians 2:13).