The Messenger of Allah ﷺ took him by the hand and said, "Muaz, by Allah, I love you. By Allah, I love you."Then he said, "I advise you, Muaz, never to fail to say at the end of every prayer, 'O Allah, help me to remember You, to thank You, and to worship You in the best manner.'"Muaz passed on this advice to Sanabihi, and Sanabihi passed it on to Abu Abdul-Rahman.
حدثنا عبيد الله بن عمر بن ميسرة حدثنا عبد الله بن يزيد المقرئ حدثنا حيوة بن شريح قال سمعت عقبة بن مسلم يقول حدثني أبو عبد الرحمن الحبلي عن الصنابحي
أن رسول الله ﷺ أخذ بيده وقال يا معاذ والله إني لأحبك والله إني لأحبك فقال أوصيك يا معاذ لا تدعن في دبر كل صلاة تقول اللهم أعني على ذكرك وشكرك وحسن عبادتك وأوصى بذلك معاذ الصنابحي وأوصى به الصنابحي أبا عبد الرحمن
Its isnad is sahih. Nasai narrated it in the book of Sahw, in the chapter on another type of dua, hadith no. 1304, from the hadith of Haywa bin Shurayh with the same wording. Ibn Khuzayma graded it sahih, hadith no. 751, as did Ibn Hibban, hadith no. 2345, and Hakim graded it sahih according to the criteria of the two Shaykhs, 1/273, with Dhahabi agreeing, and they both graded it sahih again at 3/273–274.