Is it permissible for a Muslim to greet a person who is praying, or engaging in dhikr, or supplicating?

It is legislated for a Muslim to greet his praying brother, and the one praying should return the greeting by gesturing, not by speech, as has been reported from Ibn Umar, Suhayb, and Umm Salamah in multiple narrations. It is also legislated for a Muslim to greet someone who is in a state of remembrance (dhikr) or supplication (du'a), based on what is established in the hadith of Abu Waqid al-Laythi regarding the entry of the three individuals, and the hadith of the Bedouin who greeted the Prophet, peace and blessings be upon him, while he was in the mosque.