“So Abram departed, as the LORD had spoken unto him; and Lot went with him: and Abram was seventy and five years old when he departed out of Haran.” (Genesis 12:4)
It is not clear from the text just how God made Himself known to Abram when He called him to go to Canaan. The language would imply that there was an audible conversation of some sort—far different from what you and I might expect today. At the time of this calling, Abram was a not then a follower of Yahweh, yet the circumstances of God’s intervention were enough to persuade Abram to uproot his family and start the journey.
Abram’s calling and initial response (Genesis 12:1-5) are analogous to an “awakening,” the initial faith to “see” God (Ephesians 2:8). There were no specifics in God’s promise, only broad terms of blessing.
Abram’s response was all that he knew to do at that time, to respond in obedience (non-resistance) just as the Scripture implies we are to do (1 Thessalonians 2:13; Titus 3:5; 1 Peter 1:2-5). Salvation is completely God’s doing; our “work” is never involved (2 Corinthians 5:21; Romans 10:8-17). All we can ever do is rebel and reject the drawing that God wields (John 6:44). Damnation is man’s work (John 3:19-21; Romans 1:18-32).
That is why Abram became the biblical example of the faithful (Galatians 3:6-9; Hebrews 11:8-10). The actual moment of Abram’s “new creation” (2 Corinthians 5:17; Ephesians 4:24) seems to have come somewhat later when he “believes God” (Genesis 15:6; Romans 4:3). Although repentance and faith may come in a rapid sequence, sometimes (especially in adult conversions) the events may be drawn out over time. Either way, it is by “grace are ye saved, through faith” (Ephesians 2:8).