Shiva Purana
अरुद्रो वा सरुद्रो वा सकृत्पञ्चाक्षरेण यः ॥ पूजयेत्पतितो वापि मूढो वा मुच्यते नरः ॥ १५ ॥
He who worships me even once with the five-syllabled mantra with or without the Rudra mantra is liberated even if he is a fallen or a foolish man.
english translation
arudro vA sarudro vA sakRtpaJcAkSareNa yaH ॥ pUjayetpatito vApi mUDho vA mucyate naraH ॥ 15 ॥
hk transliteration by Sanscript