Why did Abraham stay in Haran before going to the Promised Land?
Abraham remained in Haran because God halted the caravan at the upper Euphrates and kept them there until his father Terah died. Only after Terah's death did God bring Abraham down into the Promised Land. The delay likely spanned years, perhaps about twenty-five, fitting Abraham's life segments.
Les teaches that as the entourage reached the upper reaches of the Euphrates, up in Haran, north of present-day Damascus, God stopped that little caravan and kept them until Terah, Abraham's father, died. He did condescend and let Abraham keep Lot, but after Terah died, God brought Abraham down into the Promised Land. This did not all happen in a year or two; years go by, probably as much as twenty-five. Les points out that every segment of Abraham's life is divisible by five: he probably got the first call when he was 50, probably left Haran to go down into the Land of Israel when he was 75, Isaac was born when he was 100, and he died at 175. So Abraham's whole life is in segments of fives and twenty-fives. God told him to get out of his father's house and homeland and go to a land God would show him.