Judges 13 is all about the announcement of the birth of Samson- best known for his rendezvous with Delilah, which ultimately led to his downfall. The first person to receive the announcement of his birth from the angel of the Lord was Samson's mother (although the angel did visit a second time to make the announcement to both her and her husband after that). Within both announcements Samson's mother was also given a set of instructions.
By default of carrying Samson in her womb and receiving the angel's instructions, Samson's mother became a Nazirite. It wasn't enough that she was the vessel through which Samson entered the world to fulfill his purpose of "[delivering] Israel out of the hand of the Philistines". It also wouldn't have been enough for her to tell him what being a Nazirite involved. She had to show him by becoming one herself and leading by example...
