John 13:34

The commandment of mutual love had been previously given, but evidently misconstrued and abridged by the Jews to friends only, to this life only, and for earthly respects: but Jesus Christ reneweth it and enlargeth it after the form of his own love towards us, and giveth grace to observe it. (Bristow)

1. The command of their Master (v. 34): A new commandment I give unto you. He not only commends it as amiable and pleasant, not only counsels it as excellent and profitable, but commands it, and makes it one of the fundamental laws of his kingdom; it goes a-breast with the command of believing in Christ, 1 John 3 23; 1 Pet 1 22. It is the command of our ruler, who has a right to give law to us; it is the command of our Redeemer, who gives us this law in order to the curing of our spiritual diseases and the preparing of us for our eternal bliss. It is a new commandment; that is, (1.) It is a renewed commandment; it was a commandment from the beginning (1 John 2 7), as old as the law of nature, it was the second great commandment of the law of Moses; yet, because it is also one of the great commandments of the New Testament, of Christ the new Lawgiver, it is called a new commandment; it is like an old book in a new edition corrected and enlarged. This commandment has been so corrupted by the traditions of the Jewish church that when Christ revived it, and set it in a true light, it might well be called a new commandment. Laws of revenge and retaliation were so much in vogue, and self-love had so much the ascendant, that the law of brotherly love was forgotten as obsolete and out of date; so that as it came from Christ new, it was new to the people. (2.) It is an excellent command, as a new song is an excellent song, that has an uncommon gratefulness in it. (3.) It is an everlasting command; so strangely new as to be always so; as the new covenant, which shall never decay (Heb 8 13); it shall be new to eternity, when faith and hope are antiquated. (4.) As Christ gives it, it is new. Before it was, Thou shalt love thy neighbour; now it is, You shall love one another; it is pressed in a more winning way when it is thus pressed as mutual duty owing to one another.

Verses 31-35 Christ had been glorified in many miracles he wrought, yet he speaks of his being glorified now in his sufferings, as if that were more than all his other glories in his humbled state. Satisfaction was thereby made for the wrong done to God by the sin of man. We cannot now follow our Lord to his heavenly happiness, but if we truly believe in him, we shall follow him hereafter; meanwhile we must wait his time, and do his work. Before Christ left the disciples, he would give them a new commandment. They were to love each other for Christ's sake, and according to his example, seeking what might benefit others, and promoting the cause of the gospel, as one body, animated by one soul. But this commandment still appears new to many professors. Men in general notice any of Christ's words rather than these. By this it appears, that if the followers of Christ do not show love one to another, they give cause to suspect their sincerity.