A.T. Robertson Commentary Matthew 12:3

"But he said unto them, Have ye not read what David did, when he was hungry, and they that were with him;" — Matthew 12:3 (ASV)

What David did (τ εποιησεν Δαυειδ). From the necessity of hunger. The first defence made by Christ appeals to the conduct of David (2 Samuel 21:6). David and those with him did "what was not lawful" (ο ουκ εξον ην) precisely the charge made against the disciples (ο ουκ εξεστιν in verse 2).