Answered by Shaykh Amjad Rasheed
Is it a reprehensible innovation to send blessings on the Messenger between the rak`ahs of tarawih?
It is not a reprehensible innovation because sending peace and blessings on the Prophet, Allah’s peace and blessings be upon him, is one of the best forms of dhikr. Doing this frequently is a confirmed recommendation, without specification of time.
It has come in a hasan (well-authenticated) hadith, from Tirmidhi and others on the authority of Ubayy ibn Ka`b who said, “O Messenger of Allah, verily I send blessings on you frequently in my supplications, so how much of them should I dedicate to you? He said, “As much as you wish.” I said, “A quarter?”. He said, “As much as you like, the more you do, the better it is for you.” I said, “One half?” He said, “As much as you like, the more you do it is better for you.” I said, “Two-thirds?” He said, “As much as you like, the more you do, it is better for you.” I said, “I will dedicate all my supplications to you, then.” He said, “Then you will be sufficed from worry, and your sins will be forgiven.”
However, it is not permissible for a person to believe that sending blessings on the Prophet, Allah’s peace and blessings be upon him, is actually a specific sunna in this specific place, because it hasn’t been specifically established. Rather it is a general sunna, whereby it is permissible to do it at anytime, whether during tarawih or not.
Amjad Rasheed
[Translated by Sr. Shazia Ahmad]