Answered by Shaykh Faraz Rabbani
In the Hanafi school, is a person’s salat valid if they do not say the dua after Durood-e-Ibrahim (Allahuma salli ala muhammadin wa ala ali muhammad kama salayta…..)?
Walaikum assalam wa rahmatullah,
I pray that this finds you well, and in the best of health and spirits. May Allah grant you all good and success in this life and the next.
It is a confirmed sunna to make (any) supplications after sending blessings upon the Prophet (peace and blessings be upon him) before the final salams. [Haskafi, al-Durr al-Mukhtar]
Given this, omitting the supplications does not invalidate one’s prayer–though it is improper to do so. [ibid; Ibn Abidin, Radd al-Muhtar]
Any supplications from the Qur’an or Sunna fulfill this sunna. Likewise, one can make supplication with one’s own words–as long as one doesn’t ask for things one can ask other humans, as this is considered “human speech,” and the Prophet (peace and blessings be upon him) said, “No human speech befits this prayer of ours.”
And Allah alone gives success.
Faraz Rabbani