The Messenger of Allah ﷺ performed Hajj on its own.
حدثنا عبد الرحمن عن مالك عن عبد الرحمن بن القاسم عن أبيه
أن رسول الله ﷺ أفرد بالحج
No references are available.
Its isnad is sahih, but many of the companions disagreed with her, holding that the Prophet ﷺ said, "Labbayka with an umrah and a hajj together." This hadith is found in Muslim 2/875, number 1211.