I believe it shows the power of God's electing grace. Abraham delayed to come to the promised land after being called but God drew him nonetheless.
This is from ruinandredemption.com, I hope it helps:
How did Abram respond to God's call? Genesis 12:4 says, “So Abram went forth as the Lord had spoken to him. . .” But that wasn't exactly the whole story. We know this because of what Scripture records in Acts 7:2-3. In making his defense to the Sanhedrin, Stephen begins by saying, “Hear me, brethren and fathers! The God of glory appeared to our father Abraham when he was in Mesopotamia, before he lived in Haran, and said to him, 'Leave your country and your relatives, and come into the land that I will show you.' ” It seems that Abram had lived in Haran a long time (cf. 12:5). And Acts tells us that God spoke to Abram the words recorded in Genesis 12:1-3 before Abram even lived in Haran; which means that Abram did obey, but only years after God had first appeared to him. Abram followed God's call, but it took him a long time.
Well, what happened? How did Abram finally come to his senses in Haran and make the rest of the journey to Canaan? Stephen tells us in the next verse, in verse 4: “after his father died, God removed him from there [Haran] into this land in which you are now living” (ESV). What happened? “God removed him.” And by the way, the Greek word used here (Gr. metoikizo) is only used twice in Scripture; once here and then later in verse 43, where Stephen quotes from a passage in Amos that describes how God would send Israel into exile for their sins: “I will remove you beyond Babylon.” That's a violent removal. And yet that's the same word that's being used here for how it was that God brought Abram into Canaan! Ultimately, God did it—God caused Abram to leave Haran and come into the land of promise. God didn't just call Abram to the land of promise—He drew Abram to the land of promise. There was a command, but in the Covenant of Grace, all that God requires, He also provides. This was more than a call—it was an effectual call; it was a call that Abram couldn't resist, because God himself would cause him to obey. And it's no different with us; with God's calling us to turn from our sins and believe upon Christ. If you are a believer in Jesus, you need to know that the reason you left all to follow Christ wasn't because you made a decision—it was because God made a decision. It wasn't because you chose Him but because He chose you. What we see here with Abram is the same truth Jesus spoke of in the gospels: “Many are called, but few are chosen.”
A side about Terah: Why didn't Terah make it all the way to Canaan? What happened? His name might give us a hint. In Hebrew, Terah means “delay.” Terah delayed. He went half way, but never made it home. . .
