Sunan Ibn Majah Book 33, Hadith 144
"I heard the Messenger of Allah (ﷺ) say: 'The best of remembrance is La ilaha illallah (None has the right to be worshipped but Allah), and the best of supplication is Al-Hamdu Lillah (praise is to Allah).'"
the Prophet(ﷺ) said: "Whoever says, following the morning prayer: La ilaha illallahu wahdahu la sahrikalau, lahul mulku wa lahul hamdu, bi yadihil khair, wa huwa ala kulli shay'in qadir (None has the right to be worshipped but Allah alone, with no partner or associate. His is the dominion, all praise is to Him, in His Hand is all goodness, and He is Able to do all things), it will be as if he freed slave from among the sons of Isma'il."
the Messenger of Allah (ﷺ) told them: "One of the slaves of Allah said: 'Ya Rabb! Lakal-hamdu kama yanbagi li-jalali Wajhika wa li 'azima sultanika (O Lord, to You is praise as befits the Glory of Your Face and the greatness of Your Might.)' The angels were uncertain and did not know how to write this down, so they ascended to heaven and said: 'O our Lord, Your slave has said a word that we do not know how to write down.' Allah said - and He knows best what His slave said - 'What did My slave say?' They said: 'O Lord, he said "Ya Rabb! Lakal-hamdu kama yanbagi li-jalali Wajhika wa li'azima sultanika (O Lord, to You is praise as befits the Glory of Your Face and the greatness of your Might).'" Allah said to them: 'Write it down as My slave said it, until he meets Me and I shall reward him for it.'"