Ibn Majah

Benefits and Issues:

➊
Our esteemed researcher has declared the mentioned narration weak in its chain of transmission, whereas other scholars have graded it as authentic (sahih) or good (hasan).
A thorough discussion has been conducted on this matter,
from which the opinion favoring the authentication of the hadith appears closer to correctness. Therefore, despite the mentioned narration being weak in its chain, it is, on the basis of corroborating evidences, acceptable for practice and as proof.
For further details, see: (al-Mawsu‘ah al-Hadithiyyah, Musnad al-Imam Ahmad: 5/337, 338; Irwa’ al-Ghalil by al-Albani: 4/285, 286; Sunan Ibn Majah, edited by Dr. Bashar ‘Awwad, no. 3045)
Accordingly, since shaving the head expresses compliance with the command more clearly and perfectly,
for this reason, three supplications were made for them.

➋
Hafiz Ibn Hajar rahimahullah has transmitted this explanation from Imam Khattabi rahimahullah: among the Arabs, it was customary to keep hair, and they considered shaving the head to be the practice of non-Arabs (Ajamis), so they were disinclined to shave their heads.
The meaning is that, despite this, shaving the head is a higher level of compliance with the command.

➌
By “doubt” is meant the expression of hesitation and indecisiveness.