Reference: Siyar A’laam an-Nubalaa – Volume 1, Page 153
‘Aa.ishah (radhi-yAllaahu ‘anhaa) narrated:
The Messenger of Allaah ﷺ kissed ‘Uthmaan ibn Magh.dthoon whilst he [lay there before him] – dead, and [as he did so] his tears fell upon the cheek of ‘Uthmaan ibn Magh.dthoon.