Shiva Purana
न कदाचिन्न कस्यापि रिपुरेष महामनुः ॥ सुसिद्धो वापि सिद्धो वा साध्यो वापि भविष्यति ॥ ६८ ॥
This great mantra is never harmful to anyone. It may be either Susiddha, or Siddha or Sādhya.
english translation
na kadAcinna kasyApi ripureSa mahAmanuH ॥ susiddho vApi siddho vA sAdhyo vApi bhaviSyati ॥ 68 ॥
hk transliteration by Sanscript