كتاب الطهارة
Read the English translation first, with the original Arabic directly underneath.
Narrated Ali ibn AbuTalib:
The key to prayer is purification; its beginning is takbir and its end is taslim.
مِفْتَاحُ الصَّلاَةِ الطُّهُورُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ