Shiva Purana
अजानन्नहनद्बभ्रोश्शिरश्शार्दूलशंकया ॥ निश्चक्राम सभीर्व्याघ्रो दृष्ट्वा तं खड्गिनं प्रभुम् ॥ ५५ ॥
On seeing the lord armed with a sword the frightened tiger slipped away. Not knowing it and mistaking a reddish brown cow as the tiger he hit it with his sword on its head.
english translation
ajAnannahanadbabhrozzirazzArdUlazaMkayA ॥ nizcakrAma sabhIrvyAghro dRSTvA taM khaDginaM prabhum ॥ 55 ॥
hk transliteration by Sanscript