Matthew 3:15

Thus it becometh us - It is suitable and proper. And though you may feel yourself unworthy, yet it is proper it should be done.

All righteousness - There was no particular precept in the Old Testament requiring this, but he chose to give the sanction of his example to the baptism of John, as to a divine ordinance. The phrase “all righteousness,” here, is the same as a righteous institution or appointment. Jesus had no sin. But he was about to enter on his great work. It was proper that he should be set apart by his forerunner, and show his connection with him, and give his approbation to what John had done. He submitted to the ordinance of baptism, also, in order that occasion might be taken, at the commencement of his work, for God publicly to declare his approbation of him, and his solemn appointment to the office of the Messiah.