´It was narrated from Abu Sa'eed Al-Khudri that:` 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."
Related hadith on this topic
Explanation & Benefits
Shaykh Dr. Abdur Rahman Freywai
1:
That is:
When the Prophet (sallallahu alayhi wa sallam) said, "Its conclusion is the taslim (salutation of peace),"
this statement will not be interpreted in any other sense.
Note:
(In the chain of narration, Sufyan ibn Waki‘ is saqit al-hadith (unreliable in hadith),
and Tarif ibn Shihab Abu Sufyan Sa‘di is weak,
but this hadith is strengthened by the hadith of Ali (radi Allahu anhu) (no. 3), and thus it is authentic.)
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 238