Mu'awiyah wrote to Al-Mughirah asking him to write him a hadith that he had heard from the Messenger of Allah ﷺ. Al-Mughirah wrote to him (Saying): "I heard him say, when he finished the prayer: 'La Ilaha Illallah wahdahu la sharika lah, lahul-mulk wa lahul-hamd wa huwa 'ala kulli shay'in qadir (There is none worthy of worship except Allah ﷺ alone with no partner or associate. He is the Dominion and to Him be all praise, and He is able to do all things) three times." (Using translation from Nasāʾī 1343)   

أنِ اكْتُبْ إِلَيَّ بِحَدِيثٍ سَمِعْتَهُ مِنْ رَسُولِ اللهِ ﷺ فَكَتَبَ إِلَيْهِ الْمُغِيرَةُ إِنِّي سَمِعْتُهُ يَقُولُ عِنْدَ انْصِرَافِهِ مِنَ الصَّلَاةِ «لَا إِلَهَ إِلَّا اللهُ وَحْدَهُ لَا شَرِيكَ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ» ثَلَاثَ مَرَّاتٍ خَالَفَهُ أَبُو عَوَانَةَ الْوَضَّاحُ رَوَاهُ عَنْ مُغِيرَةَ عَنْ شِبَاكٍ عَنِ الشَّعْبِيِّ عَنِ الْمُغِيرَةِ وَلَمْ يَذْكُرْ وَرَّادًا  

(the freed slave of Al-Mughira bin Shuʿba) Al-Mughira wrote to Muawiya bin Abu Sufyan that Messenger of Allah ﷺ used to say at the end of every prayer after the Taslim, "La ilaha illa-l-lahu wahdahu la sharika lahu; lahu-l-mulk wa lahu-l-hamd, wahuwa 'ala kulli shai'n qadir. Allahumma la mani'a Lima a taita, wa la mu'ta Lima mana'ta, wa la yanfa'u dhal-jaddu minkal-jadd. (Using translation from Bukhārī 6330)   

سَمِعْتَ رَسُولَ اللهِ ﷺ يَقُولُ فِي دُبُرِ الصَّلَاةِ قَالَ سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ فِي دُبُرِ الصَّلَاةِ «لَا إِلَهَ إِلَّا اللهُ وَحْدَهُ لَا شَرِيكَ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ اللهُمَّ لَا مَانِعَ لِمَا أَعْطَيْتَ وَلَا مُعْطِيَ لِمَا مَنَعْتَ وَلَا يَنْفَعُ ذَا الْجَدِّ مِنْكَ الْجَدُّ»