‘Now the apostles and the brethren who were in Judaea heard that the Gentiles also had received the word of God.'
The news had reached the ears of the Apostles and their fellow-brethren in Judaea and Jerusalem of what Peter was purported to have done. Through him Gentiles had ‘received the word of God', that is had been accepted as those who had responded to Christ and His word.
That they had received the word of God was good if it was in the right way, by them standing on the edge of the crowds and listening to the preaching, and going away and thinking about it and acting on it personally. But the question was. Had Peter really taken it so far as to be willing to enter their unclean houses in order to reach them? (He had after all stayed with a tanner which might be seen as implying that he was a little careless about such things).
No mention is made anywhere in the enquiry about the fact that the Gentiles had been baptised. But baptising people did not actually contravene any specific Mosaic laws, and they may even not yet have realised that it had happened. What concerned them was the maintenance of the purity of Judaistic Christianity in Jewish terms, in terms accepted by all, a purity they saw as having been tarnished.