Why did God send Saul into the desert in Arabia after his conversion?
God sent Saul into the desert in Arabia so that He could reveal the doctrines of grace to him over what is understood to be a three-year period. This took place immediately after Saul's conversion, during which God also commissioned Peter to go to Cornelius.
Les teaches that immediately after Saul's conversion, God sent him out into the desert in Arabia. There, over what Les understands to be a three-year period, God was going to reveal the doctrines of grace to him. During that same time, God commissioned Peter to go up to the house of Cornelius. Les stresses that Acts chapter 10 follows chapter 9 in content, not merely numerically, and that this order makes everything fit. Had chapter 10's events occurred before Saul's conversion, Les says he could not teach the way he teaches. Saul was converted in chapter 9 as the head of that long line of sinners saved by grace, and then God sent Peter to a Gentile house. Peter had to admit that God was saving Gentiles without bringing them into contact with Judaism. This carried on the transition out of Judaism and God's dealing with Israel, as He now turned to the Gentiles.