Is there an authentic Hadith stating that prayer without a sutrah diminishes the reward by half?

There is no religious text stating that the reward for praying without a sutrah is reduced by half; rather, this is an interpretation by some scholars. There are hadith (definition) that command the use of a sutrah and warn against Satan interrupting the prayer, such as the Prophet's (peace be upon him) saying: "When one of you prays towards a sutrah, let him draw near to it, so that Satan does not interrupt his prayer."

Scholars interpret this hadith to mean that the sutrah prevents Satan from whispering and removing khushu' (devotion). It was narrated from Ibn Mas'ud that whoever passes in front of a praying person has half of his prayer’s reward removed, and this indicates a reduction in reward. Scholars agree on the validity of prayer without a sutrah, though its reward is diminished, but there is no evidence to indicate that this reduction amounts to half of the reward.