And reflect in His, the Most High's wisdom in making the kings of the servants, their leaders and their rulers to be of the same type as the actions [of the servants].
Imām Aḥmad (along with Imām Mālik) was upon the view of negating contagion [as a matter of superstition] and eating with the sick (leper) with trust upon Allāh.
The twins differing health patterns present a mystery. Why did one become ill with a childhood disease, like measles for example, while the other did not?
The people of Islām are strangers amongst mankind. And the believers are strangers amongst the people of Islām. And the people of knowledge are strangers amongst the believers.