Sahih Al-Bukhari — Hadith #744

Allah's Messenger (ﷺ) used to keep silent between the Takbir and the recitation of Qur'an and that interval of silence used to be a short one. I said to the Prophet (ﷺ) "May my parents be sacrificed for you! What do you say in the pause between Takbir and recitation?" The Prophet (ﷺ) said, "I say, 'Allahumma, baa`id baini wa baina khatayaya kama baa`adta baina l-mashriqi wa l-maghrib. Allahumma, naqqini min khatayaya kama yunaqqa th-thawbu l-abyadu mina d-danas. Allahumma, ighsil khatayaya bi l-maa'i wa th-thalji wa l-barad (O Allah! Set me apart from my sins (faults) as the East and West are set apart from each other and clean me from sins as a white garment is cleaned of dirt (after thorough washing). O Allah! Wash off my sins with water, snow and hail.)"