Musannaf Ibn Abi Shaybah

Hazrat Hisham states that Hasan Basri, regarding those people who wish to seek permission, said: If even one person among them says, "Assalamu Alaikum. May we enter?" then this will suffice on behalf of all of them.

Hazrat Mughira narrates that we came to Hazrat Abu Razin in such a state that we were in large numbers, and each one of us was greeting and seeking permission. Upon this, he said: Indeed, when permission has been granted to the first among you, then permission has been granted to all the rest as well.