Theophylact of Ohrid

"Everyone who asks receives." Does the one who asks for useless things receive? No. For, first of all, a request for useless things cannot even be called a request before God. For whoever prays to God must ask for what He gives. And if someone asks for useless things, he makes his request not to God, for He does not give what is not beneficial.

Commentary on Luke ↗

Cyprian

These things we suffer by our own fault and our own deserving, even as the divine judgment has forewarned us, saying, "If they forsake my law and walk not in my judgments, if they profane my statutes and keep not my commandments, then will I visit their transgressions with the rod, and their iniquities with stripes." It is for this reason that we feel the rods and the stripes, because we neither please God with good deeds nor atone for our sins. …

Epistle VII ↗

Bede

For everyone (he says) who asks receives, and he who seeks finds, and to him who knocks it will be opened. Therefore, according to the previous parable of the requesting friend, perseverance is required so that we may receive what we ask, find what we seek, and have opened what we knock on. For if it is given to the one who asks, and the seeker finds, and it is opened to the one who knocks, therefore, to whom it is not given, who does not find, and to whom it is not opened, it is clear that he did not ask, seek, or knock properly.

On the Gospel of Luke ↗

Bonaventure

Second, with respect to the exhortation regarding all, he adds: For everyone who asks receives, if he devoutly asks. Whence the Lord intimates this in John 15: "If you shall ask the Father anything in my name, he will give it to you," that is, for your salvation; otherwise he does not give. …

Commentary on Luke, Chapter 11 ↗