Commendations of Love
The Apostle Peter, likewise, says, “And, above all things, have fervent love among yourselves: for love shall cover the multitude of sins.” The Apostle James also says, “If you fulfil the royal law, according to the Scripture, You shall love your neighbour as yourself, you do well.” So also the Apostle John says, “He that loves his brother abides in the right;” again, in another passage, “Whosoever does not righteousness is not of God, neither he that loves not his brother; for this is the message which we have heard from the beginning, that we should love one another.” Then he says again, “This is His commandment, that we should believe in the name of His Son Jesus Christ, and love one another.” Once more: “And this commandment have we from Him that he who loves God love his brother also.” Then shortly afterwards he adds, “By this we know that we love the children of God, when we love God, and keep His commandments; for this is the love of God, that we keep His commandments: and His commandments are not grievous.” While, in his second Epistle, it is written, “Not as though I wrote a new commandment unto you, but that which we had from the beginning, that we love one another.”
Source: On Grace and Free Will (New Advent)