I was with Ibn Umar at Mina when he passed by a man who was slaughtering his sacrificial camel while it was kneeling. He said, "Make it stand with its leg tied. That is the sunnah of Muhammad ﷺ."
حدثنا أحمد بن حنبل حدثنا هشيم أخبرنا يونس أخبرني
كنت مع ابن عمر بمنى فمر برجل وهو ينحر بدنته وهي باركة فقال ابعثها قياما مقيدة سنة محمد ﷺ
Bukhari narrated it in Hajj, chapter on slaughtering camels while hobbled, no. 1713, and Muslim in Hajj, chapter on the recommendation of slaughtering camels while standing and hobbled, no. 1320, from the hadith of Yunus through the same chain.