John Chrysostom

"This was done thrice: and the vessel was received up again into heaven." For, that it may not seem to be a mere fancy, "this was done thrice." And yet it was the same Lord that had discoursed above in the Law concerning things clean and unclean. But in that sheet were also all the four-footed beasts of the earth: the clean with the unclean.

Homily on Acts 22 ↗

Theophylact of Ohrid

And that three times he confessed that the animals there were unclean. And the fact that the vessel descended from heaven and ascended back there — this is a great proof of purity. So this is accomplished for those to whom it is to be told.

Commentary on Acts ↗

Bede

Now this happened three times, because the mystery of the Holy Trinity was to be preached by the twelve apostles to the four parts of the world, therefore four lines were let down from heaven a third time. Or as blessed Ambrose interprets, the figure repeated three times expressed the operation of the Trinity. And therefore, in mysteries, a triple question is put forth and a triple confirmation is celebrated, nor can anyone be purified except by a triple confession. …

Commentary on Acts ↗