This question explains why Jesus will not call for the angels. Gill spells it out: if a host of angels rescued Him, how could the Scriptures be fulfilled, the ones "which speak of Christ's being taken, and led as a lamb to the slaughter, and of his various sufferings"? Barnes says Jesus meant "the Scriptures which foretold of his dying for the world," and that He said it "to comfort his disciples; to show them that his death was not a matter of surprise or disappointment to him; and that they, therefore, should not be offended and forsake him." Earlier that night He had quoted one such Scripture: "I will smite the shepherd, and the sheep of the flock shall be scattered abroad" (Matthew 26:31).

Matthew gives the answer in the next verses: "But all this was done, that the scriptures of the prophets might be fulfilled" (Matthew 26:56). Mark records Jesus saying, "but the scriptures must be fulfilled" (Mark 14:49). Then the Scripture Jesus had quoted came true before their eyes: "Then all the disciples forsook him, and fled" (Matthew 26:56; compare Matthew 26:31).

The phrase "it must be" translates the Greek dei, a word of necessity: it has to happen. Jesus is not saying events forced His hand, but that what God had spoken must come to pass.

Gill lists many Old Testament passages Jesus may have had in mind. Among them are Isaiah 53:7, where the Servant "is brought as a lamb to the slaughter," Isaiah 53:12, where "he was numbered with the transgressors," and Zechariah 13:7, the smitten shepherd that Jesus Himself quoted that night (Matthew 26:31).

Jesus let God's word decide His path, even when the word led to suffering. Matthew Henry draws the lesson: "In all difficult cases, the word of God must be conclusive against our own counsels, and nothing must be done, nothing attempted, against the fulfilling of the scripture." The cross was not a detour from God's plan. It was the plan written long before.

After He rose, Jesus asked two of His disciples, "Ought not Christ to have suffered these things, and to enter into his glory?" and then explained "in all the scriptures the things concerning himself" (Luke 24:26-27). The question asked in Gethsemane was answered after the resurrection: the suffering the Scriptures foretold led to the glory they also promised.