Hadith.2837 - Ibn Muskan narrated from al-Hudhayl, from Abu Abdullah (as), regarding a man who relies on counting the circuits of his companion during Tawaf (circumambulation) and whether it suffices for both of them and for a child.
Imam (as) replied
"Yes. Do you not see that you follow the Imam in prayer when you pray behind him? It is similar to that."