Albert Barnes Commentary Luke 2:17

"And when they saw it, they made known concerning the saying which was spoken to them about this child." — Luke 2:17 (ASV)

When they had seen it. When they had convinced themselves of the truth of the Messiah's coming, and had confirmed that they could not have been mistaken in the angels' appearance. There was enough evidence to satisfy them that what the angels said was true, or they would not have gone to Bethlehem.

Having seen the child themselves, they now had evidence that would satisfy others. Accordingly, they became the first preachers of the gospel and went and proclaimed to others that the Messiah had come. One of the first duties of those who are newly converted to God, and a duty in which they delight, is to proclaim to others what they have seen and felt.

It should be done in a proper way and at the proper time; but nothing can or should prevent a Christian recently converted from telling his feelings and views to others—to his friends, his parents, his brothers, and his old companions. And it should be noted that often more good may be done at that time than during any other period of their life. Entreaties at that time make an impression; nor can a sinner easily resist the appeals made to him by one who was only recently with him on the way to ruin, but who now treads the way to heaven.