The pairing with Parashah Naso, whose laws of the Nazirite vow set out the restrictions a person voluntarily undertakes for a set period, abstaining from wine, avoiding contact with the dead, and letting the hair grow uncut, rests on the haftarah's presentation of the same restrictions applied in an unusual way: rather than an adult choosing the vow for themselves, Samson is designated a Nazirite before he is even born, his mother instructed to follow certain of the same restrictions herself during her pregnancy.
That distinction gives the pairing its particular interest: the parashah describes the Nazirite vow as a deliberate, temporary act of devotion a person undertakes and later concludes through a specific ritual, while the haftarah shows an entire lifelong Nazirite status imposed by divine decree rather than personal choice, extending the same legal category into a much rarer and more permanent form than the parashah's own procedural instructions anticipate for the ordinary case.
The angel's refusal to give his name, calling it too wonderful to be told, also connects to the parashah's broader concern with things set apart and consecrated beyond ordinary access, the Nazirite's own hair and abstentions marking a person as specially devoted in a way parallel to how the angel's identity itself remains beyond what Manoah and his wife are permitted to know.