Sforno on Genesis 4:9/ספורנו על בראשית ד׳:ט׳

1אי הבל אחיך, “in which place did you bury him?” G’d phrased this as a question only in order to give Kayin a chance to begin the process of repentance, not because He was not perfectly aware where Kayin had buried Hevel. G’d did not want to be forced to kill someone already guilty of the death penalty.

2לא ידעתי, “I do not know.” He thought that the question concerned Hevel’s whereabouts. Seeing that Kayin had not been interested previously in G’d’s ability to know the future, or to become close to Him; such knowledge about G’d was reserved to those who are cleaving to Him.