Now therefore beware, I pray thee, and drink not wine nor strong drink, and eat not any unclean thing:

Wesley's Notes

13:4 Beware - Because the child was to be a Nazarite from the womb, ver.5, and from the conception; and because the mother's pollution extends to the child, she is enjoined from this time to observe the following rules belonging to the Nazarites. Strong drink - Under which are comprehended the other particulars mentioned, Numb 6:2 -
4. Nor eat - Any of those meats forbidden, Levit 11:1 - 47, which were forbidden to all, but especially to the Nazarites.

Matthew Henry's Concise Commentary

13:1-7 Israel did evil: then God delivered them again into the hands of the Philistines. When Israel was in this distress, Samson was born. His parents had been long childless. Many eminent persons were born of such mothers. Mercies long waited for, often prove signal mercies; and by them others may be encouraged to continue their hope in God's mercy. The angel notices her affliction. God often sends comfort to his people very seasonably, when they feel their troubles most. This deliverer of Israel must be devoted to God. Manoah's wife was satisfied that the messenger was of God. She gave her husband a particular account, both of the promise and of the precept. Husbands and wives should tell each other their experiences of communion with God, and their improvements in acquaintance with him, that they may help each other in the way that is holy.