He did this so as to make come true what God had said through the prophet Isaiah:
"Here is my servant, whom I have chosen, 1 the one I love, and with whom I am pleased. I will send my Spirit upon him, and he will announce my judgment to the nations.
References for Matthew 12:18
12.18-21 Is 42.1-4 (LXX).
He will not argue or shout, or make loud speeches in the streets.
He will not break off a bent reed, nor put out a flickering lamp. He will persist until he causes justice to triumph,
and on him all peoples will put their hope."