The correct opinion is that Salatul Tasbih is not sunnah (from the prophetic teachings), and that the hadith about it is weak for several reasons which are detailed below.

While Qiyam Al-Layl is encouraged every night, the Hadith regarding its specific virtue on the night before `Eid is either inauthentic or fabricated. Scholars have classified it as unreliable. Nevertheless, praying on this night—as on any other—remains a recommended act of worship.

There are reports attributed to the Prophet about the virtue of reading Surah Ad-Dukhan on the night before Friday, but none of them are authentic.

What is circulated about there being a story of the origin of the Tashahhud and that it happened during the ascent of our Prophet (peace and blessings of Allah be upon him) to heaven (the Mi`raj) is something for which there is no basis in Islam.