´Narrated Abu Hurairah:` "I went out with the Messenger of Allah and heard a man reciting Qul Huwa Allahu Ahad [Allahus-Samad] so the Messenger of Allah (ﷺ) said: 'It is obligatory.' I said: 'What is obligatory?' He said: 'Paradise.'"
Hadith Referenceسنن ترمذي / كتاب فضائل القرآن عن رسول الله صلى الله عليه وسلم / 2897
Hadith Gradingالألبانی:صحيح، التعليق الرغيب أيضا (2 / 224)
Hadith Takhrij«سنن النسائی/الافتتاح 69 (995) ( تحفة الأشراف : 14127) ، وط/القرآن 6 (18) ، و مسند احمد (2/536) (صحیح)»
´It was narrated that Ubaid bin Hunain, the freed slave of the family of Zaib bin Al-Khattab, said:` "I heard Abu Hurairah say: 'I came back (from a journey) with the Messenger of Allah (ﷺ) and he heard a man reciting 'Say: He is Allah, (the) One, Allah-us-Samad (the Self-Sufficient Master). He begets not, nor was He begotten. And there is none equal or comparable unto Him.' The Messenger of Allah (ﷺ) said: 'It is guaranteed.' We asked him: 'What, O Messenger of Allah?' He said: 'Paradise.'"
Hafiz Muhammad Ameen
995. Commentary: Because this surah is pure monotheism (tawhid), and the reward for tawhid is Paradise—whether it is granted at the outset or after undergoing some punishment. The Messenger of Allah sallallahu alayhi wa sallam said: «مَن كان آخِرُكلامِهِ لا إلهَإلّااللهُدخَلالجنَّةَ» “Whoever’s last words are la ilaha illallah will enter Paradise.” [سنن أبي داود، الجنائز، حدیث : 3116] Every monotheist (muwahhid) will inevitably enter Paradise, whenever that may be, and then will remain there forever.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 995