Sunan an Nasai
25
Sahih+2

It was narrated from 'Abdullah bin Abi Qatadah that his father said:"The Messenger of Allah (ﷺ) said: 'When any one of you enters Al-Khala' (the toilet), let him not touch his penis with his right hand

SahihAbu Ghuddah
SahihAl-Albani