When Jesus had come into the temple area, the chief priests and the elders of the people approached him as he was teaching and said, “By what authority are you doing these things? And who gave you this authority?”
Jesus said to them in reply, "I shall ask you one question, and if you answer it for me, then I shall tell you by what authority I do these things.
Where was John's baptism from? Was it of heavenly or of human origin?" They discussed this among themselves and said, "If we say 'Of heavenly origin,' he will say to us, 'Then why did you not believe him?'
But if we say, 'Of human origin,' we fear the crowd, for they all regard John as a prophet."
So they said to Jesus in reply, "We do not know." He himself said to them, "Neither shall I tell you by what authority I do these things."

Gospel commentary

Saint Augustine (354-430), Bishop of Hippo (North Africa) and Doctor of the Church
Discourses on the Psalms, Ps 110[109]

In truth, brethren, what God promised seemed humanly unbelievable: that starting from this mortal state in which people are corruptible, despicable, weak, dust and ashes, they would become equal to God's angels! That is why God wasn't satisfied with making a scriptural covenant for them to believe but put forward a mediator as proof of his faith: no prince, no angel or archangel, but his only Son. In this way he would point out and bestow through his own Son the way by which he would lead us to the end promised to us. Yet for God it was too small a thing that his Son should show us the way: he made of him the way (cf. Jn 14:6), the way by which you would go under his direction, the way you would follow...

How far we were from him! He who is so high and we so low! We were sick, with no hope of healing. A doctor was sent but the patient did not recognize him, “for if they had known him they would not have crucified the Lord of glory” (1Cor 2:8). But the death of the doctor has been the cure of the patient; the doctor came to visit him and died to heal him. He made those who believed in him understand he was God and man: God who created us, man who recreated us. The one was visible in him, the other hidden, and that which was hidden far exceeded what was seen... The patient has been healed by what was visible that later he might be able to see in full. God postponed this final vision by concealing it, he did not refuse it.