Whenever we came to him, meaning the Prophet ﷺ, each of us would sit wherever he reached.
حدثنا أسود بن عامر حدثنا شريك عن سماك
كنا إذا جئنا إليه يعني النبي ﷺ جلس أحدنا حيث ينتهي
Its isnad is hasan, and it is found in Abu Dawud 4/259, no. 4825, in the Book of Adab, in the commentary.