"Saith the Lord, which doeth these things." Not "saith" only, but "doeth." Why then, it was God's work. "But the question is other than this namely, what Peter spoke more plainly, whether they must be circumcised. Then why dost thou harangue about these matters?" For what the objectors asserted, was not that they must not be received upon believing, but that it must be with the Law. And upon this Peter well pleaded: but then, as this very thing above all others troubled the hearers, therefore he sets this to rights again. And observe, that which was needful to be enacted as a rule, that it is not necessary to keep the Law, this Peter introduced: but the milder part, the truth which was received of old, this James saith, and dwells upon that concerning which nothing is written, in order that having soothed their minds by that which is acknowledged, he may opportunely introduce this likewise.
Source: Homily on Acts 33