It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The key to the prayer is purification, what makes (worldly acts) forbidden in it is the takbir, and what makes them permissible again is the taslim (salam)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3373
Hadith Gradingمحدثین:صحيح لصغيره
Hadith Takhrij«صحيح لصغيره۔ مضي تخريج في الحديث 2261»