10 In the earliest times, “the Holy Ghost fell upon them that believed: and they spoke with tongues,” which they had not learned, “as the Spirit gave them utterance.” These were signs adapted to the time. For there behooved to be that betokening of the Holy Spirit in all tongues, to show that the Gospel of God was to run through all tongues over the whole earth. That thing was done for a betokening, and it passed away. In the laying on of hands now, that persons may receive the Holy Ghost, do we look that they should speak with tongues?
Or when we laid the hand on these infants, did each one of you look to see whether they would speak with tongues, and, when he saw that they did not speak with tongues, was any of you so wrong-minded as to say, These have not received the Holy Ghost; for, had they received, they would speak with tongues as was the case in those times? If then the witness of the presence of the Holy Ghost be not now given through these miracles, by what is it given, by what does one get to know that he has received the Holy Ghost?
Let him question his own heart. If he love his brother the Spirit of God dwells in him. Let him see, let him prove himself before the eyes of God, let him see whether there be in him the love of peace and unity, the love of the Church that is spread over the whole earth. Let him not rest only in his loving the brother whom he has before his eyes, for we have many brethren whom we do not see, and in the unity of the Spirit we are joined to them. What marvel that they are not with us?
We are in one body, we have one Head, in heaven. Brethren, our two eyes do not see each other; as one may say, they do not know each other. But in the charity of the bodily frame do they not know each other? For, to show you that in the charity which knits them together they do know each other; when both eyes are open, the right may not rest on some object, on which the left shall not rest likewise. Direct the glance of the right eye without the other, if you can. Together they meet in one object, together they are directed to one object: their aim is one, their places diverse.
If then all who with you love God have one aim with you, heed not that in the body you are separated in place; the eyesight of the heart you have alike fixed on the light of truth. Then if you would know that you have received the Spirit, question your heart: lest haply you have the sacrament, and have not the virtue of the sacrament. Question your heart. If love of your brethren be there, set your mind at rest. There cannot be love without the Spirit of God: since Paul cries, “The love of God is shed abroad in your hearts by the Holy Spirit which is given unto us.”
Source: Homilies on the First Epistle of John (New Advent)