5 “He that has my commmandments,” He adds, “and keeps them, he it is that loves me.” He that has [them] in his memory, and keeps them in his life; who has them orally, and keeps them morally; who has them in the ear, and keeps them in deed; or who has them in deed, and keeps them by perseverance;— “he it is,” He says, “that loves me.” By works is love made manifest as no fruitless application of a name. “And he that loves me,” He says, “shall be loved of my Father, and I will love him, and will manifest myself to him.”
But what is this, “I will love”? Is it as if He were then only to love, and loves not at present? Surely not. For how could the Father love us apart from the Son, or the Son apart from the Father? Working as They do inseparably, how can They love apart? But He said, “I will love him,” in reference to that which follows, “and I will manifest myself to him.” “I will love, and will manifest;” that is, I will love to the very extent of manifesting. For this has been the present aim of His love, that we may believe, and keep hold of the commandment of faith; but then His love will have this for its object, that we may see, and get that very sight as the reward of our faith: for we also love now, by believing in that which we shall see hereafter; but then shall we love in the sight of that which now we believe.
Source: Tractates on the Gospel of John (New Advent)