The Messenger of Allah ﷺ said, "Whoever says, when he hears the muadhdhin, 'I too bear witness that there is no god but Allah alone, without partner, and that Muhammad is His servant and messenger. I am content with Allah as Lord, with Muhammad as Messenger, and with Islam as religion,' his sins will be forgiven."Qutayba narrated this to us from Layth, from al-Hakeem bin Abdullah bin Qays.
حدثنا يونس بن محمد حدثنا ليث عن الحكيم بن عبد الله بن قيس
أن رسول الله ﷺ قال من قال حين يسمع المؤذن وأنا أشهد أن لا إله إلا الله وحده لا شريك له وأن محمدا عبده ورسوله رضينا بالله ربا وبمحمد رسولا وبالإسلام دينا غفر له ذنبه حدثناه قتيبة عن ليث عن الحكيم بن عبد الله بن قيس
Its isnad is sahih. Hakeem, in the diminutive form, bin Abdullah bin Qays bin Makhrama al-Muttalibi, was a trustworthy follower who died in Egypt in the year 118. Bukhari mentioned him in Tarikh al-Kabir (2/1/88) without recording any criticism of him. In K and H, however, he is named Hakam, in the augmented form, which is an error.Ahmad's statement at the end, "Qutayba narrated it to us from Hakam bin Abdullah bin Qays," appears this way in all three original manuscripts, but it is mistaken in naming him Hakam in the augmented form. The correct name is Hakeem, in the diminutive form, though even this should not be taken entirely at face value. What is meant is that Qutayba did not narrate it directly from Hakeem, but rather narrated it from Layth bin Saad, from Hakeem. Muslim narrated it likewise (1:113), as did Abu Dawud (1:207), Tirmidhi (number 210, with our commentary), and Nasai (1:110), all of them from Qutayba, from Layth. Hakim narrated it (1:203) by the route of Qutayba, and Muslim and Ibn Majah (1:127) also narrated it from Muhammad bin Rumh, from Layth.Tirmidhi said, "This is a hasan sahih gharib hadith, we know it only through the hadith of Layth bin Saad, from Hakeem bin Abdullah bin Qays."