Albert Barnes Commentary Matthew 26:53

"Or thinkest thou that I cannot beseech my Father, and he shall even now send me more than twelve legions of angels?" — Matthew 26:53 (ASV)

Thinkest thou, etc. Jesus says that not only would Peter endanger himself, but his resistance implied a distrust of God's protection and was an improper resistance to His will. If it had been proper for them to be rescued, God could easily have furnished far more efficient aid than that of Peter—a mighty host of angels.

Twelve legions. A legion was a division of the Roman army amounting to more than six thousand men. See Barnes on Matthew 8:29.

The number twelve was mentioned, perhaps, in reference to the number of His apostles, and Himself. Since Judas was away, only eleven disciples remained. God could guard Him, and each disciple, with a legion of angels; that is, God could easily protect Him, if He were to pray to Him, and if it was His will.