Albert Barnes Commentary 1 Samuel 22:15

"Have I to-day begun to inquire of God for him? be it far from me: let not the king impute anything unto his servant, nor to all the house of my father; for thy servant knoweth nothing of all this, less or more." — 1 Samuel 22:15 (ASV)

Did I then begin ... - Some emphasize the word “begin,” as if Ahimelech’s justification was that he had often inquired of the Lord for David before, when employed on the king’s business. However, it is much better to understand the words as Ahimelech’s solemn denial of having inquired of the Lord for David on this occasion, a duty he owed to Saul alone as king of Israel. The significance of the word “begin” is that this would have been his first act of allegiance to David and defection from Saul. He strenuously repudiates this, adding that “your servant knew nothing of all this”—the conspiracy between Jonathan and David of which Saul speaks. He maintains that he acted in complete innocence.