3 But who is it that blesses the Lord at all times, except the humble in heart. For very humility taught our Lord in His Own Body and Blood: because when He commends His Own Body and Blood, He commends His Humility, in that which is written in this history, in that seeming madness of David, which we have passed by, “And his spittle ran down over his beard.” When the Apostle was read, You heard the same spittle, but running down over the beard. One says perhaps, What spittle have we heard?
Was it not read but now, where the Apostle says, “The Jews require a sign, and the Greeks seek after wisdom?” But now it was read, “But we preach,” says he, “Christ crucified” (for then He drummed), “unto the Jews a stumbling block, and unto the Greeks foolishness; but unto them which are called, both Jews and Greeks, Christ the Power of God, and the Wisdom of God. Because the Foolishness of God is wiser than men, and the Weakness of God is stronger than men.” For spittle signifies foolishness; spittle signifies weakness.
But if the Foolishness of God is wiser than men, and the Weakness of God is stronger than men; let not the spittle as it were offend you, but observe that it runs down over the beard: for as by the spittle, weakness; so by the beard, strength is signified. He covered then His Strength by the body of His Weakness, and that which without was weak, appeared as it were in spittle; but within His Divine Strength was covered as a beard. Therefore humility is commended unto us. Be humble if you would bless the Lord at all times, and that His praise should be ever in your mouth....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)