What does Judges 13:12 mean?

The "angel of the LORD," best understood as the Lord Himself, is appearing in a human form to Manoah and his wife. He has returned in response to Manoah's prayer to tell them more about how to raise the son they thought they could never have (Judges 13:2–11). The Angel seems to be waiting for Manoah to ask a question. Manoah could have demanded miraculous confirmation that this prediction was truth. That's what Gideon did (Judges 6:17; 36–40). That's what Zechariah the priest would do, a thousand years later, when an angel told him that he and his childless wife would have a baby (Luke 1:18).

Manoah, though, seems convinced that what this "angel" has said will happen. Rather than expressing doubt or insecurity, he clarifies: he wants all the information he can get. He displays this trust by beginning his question by saying "when your words come true." Then he asks what the child's life and career will be. Manoah has already heard some of this from his wife, but he seems to hope for more detail.