svanigamam apahāya mat-pratijñām
ṛtam adhikartum avapluto ratha-sthaḥ
dhṛta-ratha-caraṇo 'bhyayāc caladgur
harir iva hantum ibhaṁ gatottarīyaḥ
sva-nigamam—His own promise not to take a weapon and fight on behalf of the Pāṇḍavas; apahāya—giving up; mat-pratijñām—my promise; ṛtam—true; adhikartum—to make more; avaplutaḥ—having jumped down; ratha-sthaḥ—who was on the chariot (Lord Kṛṣṇa); dhṛta—who took up; ratha-caraṇaḥ—the wheel of the chariot; abhyayāt—ran forward; calat-guḥ—making the entire planet tremble; hariḥ—a lion; iva—like; hantum—to kill; ibham—an elephant; gata-uttarīyaḥ—losing the outer garment.
" 'Intending to make my promise true, Lord Kṛṣṇa broke His own promise not to take up a weapon at Kurukṣetra. With His outer garment falling off, Lord Śrī Kṛṣṇa jumped from His chariot, picked up a wheel and came running at me to kill me. Indeed, He rushed at me like a lion going to kill an elephant, and He caused the whole earth to tremble.'
Lord Kṛṣṇa promised not to fight in the battle of Kurukṣetra or even take up a weapon. But when Bhīṣma wanted to keep his own promise to break the promise of the Lord, the Lord immediately got down from the chariot, and to make Bhīṣma's promise true He picked up a chariot wheel and rushed forward to kill him. This is a quotation from Śrīmad-Bhāgavatam (1.9.37).
Link to this page: https://prabhupadabooks.com/cc/madhya/16/145