What is Salat al Tasbeeh

Does Salatul Tasbih have to be performed at least once in a lifetime?

There is controversy among Sunni scholars about the validity of Salatul Tasbih . The root of this dispute lies in different views about the authenticity of this hadith:

The Messenger of Allah () said to al-Abbas ibn AbdulMuttalib: Abbas, my uncle, shouldn't I give you, shouldn't I present you, shouldn't I donate to you, shouldn't I produce ten things for you? If you act according to them, Allah will forgive you of your sins, first and last, old and new, involuntary and voluntary, small and large, secret and open. These are the ten things: You should pray four rak'ahs and recite Fatihat al-Kitab and a sura in each. When you have finished reciting the first rak'ah, stand up and say fifteen times: "Glory to Allah", "Praise be to Allah", "There is no god but Allah", "Allah is greatest". Then you should bow and say ten times while bowing. Then after bowing, you should lift your head and say it ten times. Then you should prostrate yourself and say it ten times as you prostrate yourself. Then after prostrating, you should raise your head and say it ten times. Then you should prostrate yourself and say it ten times. Then after prostrating, you should raise your head and say it ten times in each rak'ah. You should do this in four rak'ahs. If you can watch it once a day, do this; if not, then once a week; if not, then once a month; if not, then once a year; If not, then once in your life.

Sunan Abi Dawud

Some scholars like Abu Dawud and Al-Albani have it as a sahih (authentic), while others like Ahmad ibn Hanbal and Ibn Taimiyah classified it as da'eef (weak). Even the scholars who do Salatul Tasbih have considered it valid, have it as Mustahab classified so that there is no sin associated with not doing it.

Source (Arabic): http://www.islamweb.net/fatwa/index.php?page=showfatwa&Option=FatwaId&Id=2501