Kālayavana, the King of Magadha and Sālva attacked the city of Mathurā, but when the city was encircled by their soldiers, the Lord refrained from killing them personally, just to show the power of His own men.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
कालमागधशाल्वादीननीकै रुन्धतः पुरम् । अजीघनत्स्वयं दिव्यं स्वपुंसां तेज आदिशत्
kālamāgadhaśālvādīnanīkai rundhataḥ puram | ajīghanatsvayaṃ divyaṃ svapuṃsāṃ teja ādiśat
SB 3.3.10