Sunan Ibn Majah 275
سنن ابن ماجه#275SahihIt was narrated from Muhammed bin Al-Hanafiyyah that his father said:"The Messenger of Allah said: 'The key to prayer is purification, its opening is to say 'Allahu Akbar' and its closing is to say As-salamu 'alaikum
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan Sahih
Muhammad Fouad Abd al-BaqiHasan Sahih
Shuaib Al ArnautHasan Lighairihi
Zubair Ali ZaiHasan
In-book reference: 1:9