Tirmidhi

English Commentary:
1:
The phrase "are not strong" pertains to the first level of the gradations of criticism (jarh).
A narration from such a transmitter is considered reliable, that is, it is capable of being strengthened, and additional narrations can be sought to support it.
It is not the case that his narration is to be disregarded altogether.
Note:
(In the chain of transmission, Harith Wajih is a weak transmitter.)

Lexical Explanation:
«أَنْقُوْا» is derived from «إِنْقَاء». It is in the imperative form. It is used in the meaning of "to purify."
«اَلْبَشَرَ» — "ba" and "sheen" have a fatha. The outer layer of a human's skin; the upper surface of a person's skin.
«وَضَعَّفَاهُ» — Both [ابوداود اور ترمذي] have declared it weak, because in its chain of narration there is a narrator, Harith bin Wajeeh, who is weak. The hadith scholars have considered his narration to be munkar (rejected).

Benefits and Issues:
➊ Although this narration is weak in its chain, the same matter is established from authentic ahadith: that in the ritual bath (ghusl) of janabah, washing the entire body is obligatory. However, regarding rinsing the mouth and putting water into the nose, the opinions of the jurists differ.
➋ According to the Hanafis, these are also included in the ruling of obligation. The well-known opinion of Imam Ahmad rahimahullah is also the same, whereas according to Imam Shafi'i rahimahullah, it is considered sunnah.
➌ In any case, in the light of the ahadith, it is clear that in the ritual bath (ghusl) of janabah, the entire body, including the hair, should be thoroughly washed and rubbed well, so that no part of the body, even as small as a hair or the area beneath the hair, remains dry without a severe necessity.