Was the dhikr mentioned in the tashahhud, "Peace be upon you, O Prophet, and the mercy of Allah," specific to the lifetime of the Prophet (peace and blessings be upon him)?

Question:
Honorable Shaykh, may Allah grant you success. In the tashahhud, we say, "Peace be upon you, O Prophet, and the mercy of Allah." He says: Was this not only during the lifetime of the Prophet (peace and blessings be upon him)? Is that correct?

Answer:
He told us what he told us (peace and blessings be upon him): Do not say this after my death. He taught them the tashahhud just as he taught them a surah from the Qur'an. In it is: "O Allah, send blessings upon [the Prophet]. Peace be upon you. Peace be upon you, O Prophet." And he did not say, "You will not see this after my death" or "It is not said." Who said this? Yes.