Sunan an Nasai
973
Sahih+2

It was narrated that Abu Sa'eed Al-Khudri said:"The Iqamah for Zuhr prayer would be said, and a person could go to the Al-Baqi', relieve himself, perform wudhu, and come (to the masjid), and the Messenger of Allah (ﷺ) would still be in the first rak'ah, making it lengthy

SahihAbu Ghuddah
SahihAl-Albani