I came with the Messenger of Allah ﷺ when he heard a man reciting "Say, He is Allah, the One. Allah, the Eternal Refuge. He neither begets nor is born, nor is there to Him any equivalent." [Ikhlas 112:1–4]The Messenger of Allah ﷺ said, "It has become certain."I asked, "What has, Messenger of Allah?"He replied, "Paradise."
أخبرنا قتيبة عن مالك عن عبيد الله بن عبد الرحمن عن عبيد بن حنين مولى آل زيد بن الخطاب قال سمعت
أقبلت مع رسول الله ﷺ فسمع رجلا يقرأ {قل هو الله أحد الله الصمد لم يلد ولم يولد ولم يكن له كفوا أحد} فقال رسول الله ﷺ وجبت فسألته ماذا يا رسول الله قال الجنة
Its chain of transmission is hasan.Tirmidhi narrated it in the Merits of the Quran, chapter on what has been said about Surah Ikhlas and Surah Izaa Zulzilat, hadith 2897, from the hadith of Malik, and he said, hasan sahih gharib. It is also found in the Muwatta (Yahya's version), 1/208, and in Kubra, hadith 1066.