They would not put their hands in the food until the Messenger of Allah ﷺ had started eating first.
حدثنا عفان حدثنا حماد بن سلمة عن حميد عن أبي المتوكل
أنهم كانوا لا يضعون أيديهم في الطعام حتى يكون رسول الله ﷺ هو يبدأ
No references are available.
Its isnad is sahih. I have not found it with this wording except in Ahmad. As for its meaning, it has come up many times before.