John Chrysostom

And besides, the sequel is enough to bear him out on this point: so now the discourse is for all in common. "But this is that which was spoken by the prophet Joel, And it shall come to pass in the last days, saith the Lord God." Nowhere as yet the name of Christ, nor His promises but the promise is that of the Father. Observe the wisdom: observe the considerate forbearance. He did not pass on to speak at once of the things relating to Christ; that He had promised this after His Crucifixion; truly that would have been to upset all. …

Homily on Acts 5 ↗

Theophylact of Ohrid

He refers not to the name of Christ, not to the promise of Christ, but to the promise of the Father. Note also the prudence of Peter. He did not pass over the prophecy in silence, but neither did he speak directly about what concerns Christ: that He, after being crucified and rising again, promised them, the apostles, this gift. If he, Peter, had said this, he would have ruined everything; although this could have proven the Divinity of Christ, it would have seemed incredible. …

Commentary on Acts ↗

Oecumenius

Then he brought forward the prophecy of Joel, nowhere mentioning Christ here, and of the signs of which they were eyewitnesses, or that this had been his promise. For if he had said this, he would have overturned everything and exposed it to scorn; but he first introduces the Father who had promised these things to them through the prophet, and removes the envy; not, he says, to the apostles only, but to every flesh, clearly to those believing sincerely, and with character. …

Commentary on Acts ↗