disc▪ Jeffery1938: »The root itself is genuine Arabic, and may be compared with Aram ṭhar ‘to be clean’, ṭyhrʔ, Syr ṭyhrā ‘brightness’, Hbr ṭāhar ‘to be clean, pure’; the SAr ṭhr in Hal, 682 (Rossini, Glossarium, 159), and the Ras Shamra ṭhr.
In its technical sense of ‘to make religiously pure’, however, there can be little doubt that it, like the Eth [Gz] ʔaṭhara and taṭāhara (Nöldeke, Neue Beiträge, 36), has been influenced by Jewish usage. It will be remembered that [Hbr] ṭhr is used frequently in Leviticus for ‘ceremonial cleanness’, and particularly in Ezekiel for ‘moral cleanliness’. Similar is its use in the Rabbinic writings, and in late passages Muḥammad’s use of the word is sometimes strikingly parallel to Rabbinic usage.«