Why did the angel come first to Mano'ach's wife?
Bamidbar Rabah 10:5: Mano'ach and his wife argued about which of them is sterile. She was a Tzadekes, and merited that the angel put Shalom between her and her husband. (Vayikra Rabah 9:9 - he did not tell Mano'ach that she is sterile, rather, she needs Samanim (medicines). 1
Malbim (13, citing Mahari): She was more prepared to see the angel than Mano'ach was.
Malbim (13): A man can impose Nezirus on his son 2 , but that has different laws. E.g. it came through a vow, so a Chacham can permit it.
Etz Yosef (9:9, 10:5): He told her that she is sterile, so she will not quarrel more with her husband; it was improper to tell Mano'ach. The pregnancy will be a total miracle. He made Mano'ach think unlike this; rather, she just needs a cure. Therefore, she must guard what she eats?
R. Yochanan (Nazir 28b): This is Halachah l'Moshe mi'Sinai. Reish Lakish holds that it is mid'Rabanan for Chinuch. (It seems that Malbim explains why the angel did not tell Mano'ach to impose Nezirus on his son. He could have appeared to Mano'ach and himself imposed Nezirus on the son! - PF)
