I once read a hadith of Imam Jafar e Sadiq a. s that if one has doubt regarding his prayer than he should offer it again but if the doubt occurs twice than he should ignore it and consider his prayer valid.
I wanted to know wether this hadith is authentic or not?

If you had a doubt in three prayers, then, it is wisswass, and you should not pay attention to it, provided that you were awake, and concentrated, while praying.