Narrated Wail ibn Hujr: I offered prayer along with the Prophet ﷺ. He would give the salutation to his right side (saying): Peace be upon you and mercy of Allah; and to his left side (saying): Peace be upon you and mercy of Allah.
Hadith Referenceسنن ابي داود / أبواب تفريع استفتاح الصلاة / 997
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:إسناده حسن
997. Commentary: «وبركاته» In the earliest manuscripts of Sunan Abu Dawood, the addition of «وبركاته» while turning the head to the right side is established, and on the left side, only saying «السلام وعليكم ورحمة الله» is established. However, in some manuscripts of Sunan Abu Dawood and in Bulugh al-Maram, the addition of «وبركاته» while turning the head for both salutations is established, from which it is understood that if a person says «وبركاته» while turning the head for both salutations, or wishes to do so, it is permissible. For details, see: [نيل الاوطار۔ 334/2، سبل السلام۔ 330۔ 331/1 اور شرح بلوغ المرام صفي الرحمٰن مبارك پوري]
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 997
Narrated Wa'il bin Hujr (RA): I prayed with the Prophet (ﷺ) and he would give the Taslim (salutation) to his right side (saying), "Peace be upon you and the mercy and blessings of Allah"; and to his left side (saying), "Peace be upon you and mercy and the blessings of Allah." [Reported by Abu Dawud, with a Sahih (authentic) chain].
➋ According to Imam Shafi‘i rahimahullah, and in fact according to the major Companions (radi Allahu anhum) and Followers (Tabi‘in), ending the prayer by saying "as-salamu ‘alaykum" is obligatory (fard). However, the Hanafis consider it only a sunnah, and they deem any act that is contrary to the prayer (i.e., that invalidates the prayer) as sufficient for exiting the prayer. But this is contrary to explicit ahadith and also opposes the verbal and practical sunnah.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 252