Fatwas of Ibn Hajar al-Haytami on 'dancing' during dhikr

<<He was asked, may Allah benefit [us] with him, about the 'dancing' (raqs) of Sufis during their emotional states (tawajud), does it have a legal basis (asl)? He replied: Yes, it does have a legal basis, it was certainly narrated in the hadith that Jaafar b. Abi Talib, Allah be well-pleased with him, 'danced' right in front of the Prophet, upon him blessings and peace [Musnad Ahmad and Sahih Ibn Hibban] due to the pleasure he experienced at hearing the Prophet address him [with the words 'You resemble me physically and morally']. It is certainly authentically narrated that a number of major imams stood up and 'danced' in the gatherings of remembrance of Allah, among them Shaykh al-Islam `Izz al-Din Ibn `Abd al-Salam.>>

Ibn Hajar al-Haytami, Fatawa Hadithiyya, Cairo: Mustafa Babi al-Halabi, 2nd ed. (p. 298).

He said something similar in a longer response in his Fatawa al-Kubra al-Fiqhiyya (4:355), also allowing the daff even inside the mosque.

Was-Salam,
GF Haddad