Waqid bin Amr bin Saad bin Muaz reported,
I attended a funeral among Banu Salama, so I stood up. Nafi bin Jubayr said to me, "Sit down, for I will inform you about this matter with reliable proof. Masud bin Hakam al-Zuraqi told me that he heard Ali bin Abu Talib 
in the courtyard of Kufa saying, 'The Messenger of Allah ﷺ had commanded us to stand for funerals, then he sat down afterwards and commanded us to sit.'"
Ahmad 623
Sahihحدثنا إسماعيل بن إبراهيم عن محمد بن عمرو قال حدثني
واقد بن عمرو بن سعد بن معاذ قال
شهدت جنازة في بني سلمة فقمت فقال لي نافع بن جبير اجلس فإني سأخبرك في هذا بثبت حدثني مسعود بن الحكم الزرقي أنه سمع علي بن أبي طالب رضي الله عنه برحبة الكوفة وهو يقول كان رسول الله ﷺ أمرنا بالقيام في الجنازة ثم جلس بعد ذلك وأمرنا بالجلوس
No references are available.
Its isnad is sahih. See 631, 1094, 1167, 1199. Muhammad bin Amr is Muhammad bin Amr bin Alqama bin Waqqas Laythi. Waqid bin Amr bin Saad was a trustworthy taabi. Nafi bin Jubayr is Nafi bin Jubayr bin Mutim. Masud bin Hakam Zurqi was a trustworthy, reliable, and firmly established taabi, born during the time of the Messenger of Allah ﷺ, and counted among the taabis and their senior figures. The hadith was narrated by Malik in Muwatta 1:232 from Yahya bin Saeed from Waqid bin Amr, and Bukhari narrated it in Tarikh al-Kabir 4/2:174-175 through other routes that go back to Masud bin Hakam. See also Muntaqa 1887.