"I testify that there is no one worthy of worship besides Allah. He is all by Himself and has no partner and I testify that Muhammad (S.A.W.) is His servant and Rasul. I am pleased with Allah as my Lord, Muhammad (S.A.W.) as my Rasul and Islam as my Deen.
It is stated in the hadith that the sins of a person are forgiven if the above dua is recited on hearing the athaan.