अहिंसा सर्वथा सर्वदा सर्वभुतानाः मनभीद्रोह।
ahiṃsā sarvathā sarvadā sarvabhutānāḥ manabhīdroha।
I read somewhere that it was written by Maharshi Veda Vyasa but the name of scripture in which he wrote it was not mentioned.
Vyasa Bhashya of Patanjali Yoga Sutras has this verse. Vyasa Muni starts commentary on Sutra 30 of Sadhana Padha with this sentence.
अहिंसासयास्तेयब्रह्मचर्यापरिग्रहा यमाः ॥ ३० ॥ (Sutra)
तत्राहिंसा सर्वथा सर्वदा सर्वभूतानामनभिद्रोहः । उत्तरे च... (Commentary)
ahiṃsāsayāsteyabrahmacaryāparigrahā yamāḥ ॥ 30 ॥
tatrāhiṃsā sarvathā sarvadā sarvabhūtānāmanabhidrohaḥ । uttare ca...
Translation by Ganganatha Jha:
Sutra (30) :—Forbearance consists in harmlessness truth, abstinence from theft, continence and freedom from avarice.
Com : Of these "harmlessness'—in no way and at no time wishing ill to any living being. The following restraints..