Abu Dawud

Benefits and Issues:
Hazrat Zayd ibn Harithah radi Allahu anhu was the mawla (freed slave) of the Messenger of Allah sallallahu alayhi wa sallam, and in the early days of Islam, he was also referred to as his adopted son.
His son, Hazrat Usamah radi Allahu anhu, was extremely beloved to the Messenger of Allah sallallahu alayhi wa sallam.
His very title became "Hibbu Rasulillah" (the darling and beloved of the Messenger of Allah sallallahu alayhi wa sallam).
There was a difference in complexion between father and son because Usamah’s mother, Umm Ayman, was Abyssinian.
He inherited her complexion, so many ignorant people would cast aspersions on his lineage, which was a source of pain for the Messenger of Allah sallallahu alayhi wa sallam and the Muslims.
Mujazziz al-Mudliji, from the well-known tribe of Banu Asad, was a renowned expert in physiognomy, and the polytheists accepted his word.
While passing by, he saw both father and son, their faces covered and their feet bare.
So, perhaps to display his scholarly authority, he remarked, “These feet are of a father and son.”
This statement became a means of affirmation and strengthening of the truth for the Muslims, and a removal of doubts.
This brought happiness to the Messenger of Allah sallallahu alayhi wa sallam and the Muslims, that a person respected by the disbelievers was refuting their own accusations.
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The juristic inference from this incident is that if, in some case, several people claim a child, or if, due to some suspicion, two or three individuals have had intercourse with a woman and it is not clear whose child it is, then a decision can be made based on the opinion of an expert and just physiognomist.
If this knowledge were entirely baseless, the Messenger of Allah sallallahu alayhi wa sallam would not have expressed happiness at his statement.
In the previous hadith of li'an (Hadith: 2252), it was mentioned that the Messenger of Allah sallallahu alayhi wa sallam said that if the child is like this, then he will belong to so-and-so.
This is evidence for the validity of the science of physiognomy.
Also, in the hadith of Umm Sulaym radi Allahu anha, it is mentioned: “If a woman does not experience a wet dream, then how does the child resemble her?” (Sahih Bukhari, al-‘Ilm, Hadith: 130 and Sahih Muslim, al-Hayd, Hadith: 313)