At that time: Jesus said to his disciples: “If anyone love me, he will keep my word, and my Father will love him, and we will come to him, and make our abode with him.” And so forth. John 14:23-31.
Homily of St Gregory, Pope
It would be well, beloved brethren, to consider briefly the words of the lesson from the Gospel, that afterwards we may have more time to spend on the consideration of this great festival [Pentecost]. Today the Holy Spirit, suddenly with a sound, came down on the disciples and changed their carnal minds, filling them with love for himself; and while outwardly fiery tongues appeared, inwardly their hearts were kindled into flame; for while they received the presence of God in the form of fire, the flames of his love engulfed them. The Holy Spirit himself is love, and so John says: “God is love.” He, then, that desires God with all his mind, in truth already possesses him whom he loves. Neither can anyone love God, if he does not possess him whom he loves.
The Holy Spirit is love
But behold, if anyone of you were asked whether he loved God, he would reply with confidence and conviction of mind: “I do.” But in the very beginning of this lesson you have heard what the Truth himself says: “If anyone love me, he will keep my word.” The test of love, then, is whether it is shown in works. And so in his epistle St John says again: “He who says, ‘I love God,’ and does not keep his commandments is a liar.” For then do we truly love God and keep his commandments, if we deny ourselves the gratification of our appetites. He who still abandons himself to unlawful desires, certainly does not love God, since of his own will he opposes him.
Preparing the house
“And my Father will love him, and we will come to him and will make our abode with him.” Consider, beloved brethren, what a great honour it is to have God coming into our hearts as a guest. Indeed, if some rich or powerful friend were entering our house, we should make all haste to have the house cleaned throughout, lest he should see something that would displease him. Let the one, then, who is preparing the house of his mind to receive God, cleanse it from all the filth of evil works. But mark what the Truth himself says: “We will come and make our abode with him.” For there are some, whose hearts he enters, but does not abide there. This is because, although they have been brought to acknowledge God on account of something that has pricked them with remorse, yet in time of temptation, they forget that very thing for which their conscience pricked them, and so they return to renew those offences as though they had never repented.
– From: An Approved English Translation of the Breviarium Romanum, Burns & Oates, London, 1964