Ibn Majah

Commentary:
(1)
Our esteemed researcher has declared this narration weak in terms of its chain of transmission, and further written that the following narration suffices in its stead. In addition, Shaykh al-Albani rahimahullah has declared this narration to be authentic. See: (al-Rawd al-Nadhir fi al-Tartib wa Takhrij Mu‘jam al-Tabarani al-Saghir, no. 475)
In any case, this narration is admissible as evidence.

(2)
Imam Ibn al-Athir has explained the term “khilal” in his book al-Nihayah as follows:
(al-takhleel tafreequ sha‘r al-lihyah wa asabi‘ al-yadayn wa al-rijlayn fi al-wudu’) (al-Nihayah fi Gharib al-Hadith wa al-Athar: 2/73, under the entry “khalal”)
The meaning of khilal is to run the fingers through the beard hair and the fingers of the hands and feet during ablution (wudu).
The purpose of this is that water reaches as much of the parts of ablution as possible.

(3)
Imam Ibn al-Qayyim rahimahullah said:
The Prophet sallallahu alayhi wa sallam would sometimes perform khilal of the beard and did not make it obligatory.
...
Similarly, he sallallahu alayhi wa sallam did not always perform khilal of the fingers. (Zad al-Ma‘ad: 1/68, Egypt print, Chapter: His Guidance in Ablution)
However, he did not mention any evidence for doing it occasionally; rather, in some narrations, there is an explicit command, from which the aspect of continuity appears to be more preponderant.
And Allah knows best.