Why did she not tell Mano'ach that she is sterile?
Malbim citing Vayikra Rabah 9:9: This was due to Shalom. 1
Why did she not tell Mano'ach that a razor may not come on the child?
Malbim: This is included in "Ki Nazir Elokim Yihyeh ha'Na'ar."
Why did she not tell Mano'ach that the child will start to save Yisrael?
Malbim: The Pelishtim were ruling, and she feared that if the matter is known, they will kill the child.
Why did she say "Ad Yom Moso"? The angel did not say so!
Mahari Kara (7,8): The angel told her, just the Navi was concise above, and taught it only here. 1 This was a prophecy that even on the day of his death, his Nezirus will help to avenge the Pelishtim; when his hair began sprouting, his strength returned.
Malbim: The angel implied so (and she correctly understood that he is commanded his entire life), but he did not say so explicitly, for he knew that before his death Shimshon will profane his Nezirus.
Mahari Kara: Throughout Tanach, matters are abbreviated in one place and explained elsewhere.
