He was also asked:

Concerning a man who prays behind an imam and sits briefly to rest between units of prayer, although the imam does not do so: is this permissible for him? If it is permissible, does it diminish his reward because he has not kept pace with the imam?

He answered:

It is established in the Sahīh collection that the Prophet, may Allah bless him and grant him peace, observed this brief sitting for rest. However, scholars have differed over whether he did so out of need owing to advanced age, or because it is part of the Sunnah of prayer.

Those who hold the latter view consider it recommended. This is the position of al-Shāfiʿī and of Ahmad according to one of the two reports from him. Those who hold the former view consider it recommended only when needed. This is the position of Abū Hanīfah, Mālik, and Ahmad according to the other report.

Anyone who observes it is not to be censured, even when praying behind an imam. According to those who consider it recommended, a delay of this duration does not constitute the prohibited lagging behind the imam. Is this not simply an action in a matter open to scholarly judgment? For him, performing this act, which he regards as Sunnah, conflicts with promptly following the imam.