John Chrysostom

What then saith Christ? He said not, "yea, it is easier, and so do," lest they should suppose that the thing is a law; but He subjoined, "Not all men receive it, but they to whom it is given," raising the thing, and showing that it is great, and in this way drawing them on, and urging them. But see herein a contradiction. For He indeed saith this is a great thing; but they, that it is easier. …

Homily on the Gospel of Matthew 62 ↗

Theophylact of Ohrid

But He said unto them, Not all can receive this saying, save they to whom it is given. Since the disciples had said that it would be better not to enter into marriage, the Lord says that virginity is a great thing but not everyone can achieve it, but only those with whom God acts in synergy. "They to whom it is given" refers to those with whom God acts in synergy. It is given to those who ask. For He says, "Ask, and it shall be given you. For everyone that asketh receiveth" (Lk. 11:9).

Commentary on Matthew ↗

Jerome

He said to them: Not everyone can understand this word, but only those to whom it is given. No one should think that under this word, either fate or fortune is introduced: these are the virgins to whom it has been given by God, or whom certain circumstances have brought to this, but it has been given to those who have asked, who have desired, who have worked to receive it. For everyone who asks will receive, and the one who seeks will find, and to the one who knocks, it will be opened (Matthew 7:8 and Luke 11:10).

Commentary on Matthew ↗

Thomas Aquinas

Who said to them: he approves the opinion of the disciples. And first by words; secondly by deeds, at then were little children presented to him. And first he approves continence; secondly he assigns the differences among the continent, at for there are eunuchs etc.; thirdly the difficulty, at he that can take, let him take it. He says therefore who said to them: all men take not this word. …

Commentary on Matthew ↗