Shiva Purana
षडक्षरेण वा देवं सूक्तमन्त्रेण पूजयेत् ॥ शिवभक्तो जितक्रोधो ह्यलब्धो लब्ध एव च ॥ १० ॥
A devotee of Śiva who has conquered anger, whether he has or has not secured grace shall worship the lord with the Sūktamantra or the six-syllabled mantra.
english translation
SaDakSareNa vA devaM sUktamantreNa pUjayet ॥ zivabhakto jitakrodho hyalabdho labdha eva ca ॥ 10 ॥
hk transliteration by Sanscript