‘ So Manoah took the kid with the meal offering, and offered it on the rock to Yahweh, and the angel did wondrously and Manoah and his wife looked on.'
Manoah offered the kid and the meal offering on the rock to Yahweh at the direct command of the Angel of Yahweh. Compare and contrast Judges 6:20-21 where Gideon did not offer the sacrifice but stood by and watched the Angel do it. Here Manoah himself offered the burnt offering. There was no altar which suggests it was not his regular custom. It is possible that he was a priest, for although ‘related' to the family of the Danites (Judges 13:2) he may have been a priest from a priestly family living among them and adopted by the tribe, a Danite Levite. Alternately under the Angel's instruction he may have been a priest for the day. Either way this was a unique offering in a place where Yahweh had revealed Himself, offered under His direct instruction. It was not a pattern for others.
“And the angel did wonderfully.” His name was wonderful (Judges 13:18) and He behaved wonderfully. He performed a mighty wonder in front of them, inspiring awe and worship. The writer stresses that Manoah and his wife were witnesses to it. These are not just tales. The writer wants us to know that they did happen in front of reliable witnesses.