SB 1.9 - Kṛṣṇa keeps Bhīṣma's promise by breaking His own
Duryodhana criticized Bhīṣma alleging that he was reluctant to kill Arjuna because of paternal affection. Angered by the insult, Bhīṣma vowed that the next day he would kill all the five Pāṇḍavas with special weapons made for the purpose. Duryodhana was satisfied and he kept the arrows with him to be delivered the next day. By tricks Arjuna took the arrows from Duryodhana, and Bhīṣma learning this, took a vow that the next day Kṛṣṇa would have to take up weapons Himself, otherwise His friend Arjuna would die. Kṛṣṇa had vowed before the battle that He would not take up weapons. The next day Bhīṣma fought so violently that both Arjuna and Kṛṣṇa were in trouble.
At that time, in order to please His devotee, Bhīṣma, by keeping Bhīṣma’s promise, Kṛṣṇa got down from the chariot, took up the wheel of the chariot and rushed at Bhīṣma in an angry mood. Kṛṣṇa, situated on the chariot, quickly got down from the chariot in such a manner that no one could see it. Or Kṛṣṇa, though He got down, remained on the chariot to protect it in another form invisible to others. He dropped His outer garment on the way. While rushing this way, Kṛṣṇa trampled the earth and the earth trembled because Kṛṣṇa allowed the weight of the entire universe to rest in His body. Bhīṣma at once gave up his weapons and stood to be killed by his beloved Lord. The fighting of the day ended at that very moment, and Arjuna was saved. Of course Arjuna could not have been killed because Kṛṣṇa was on the chariot. To keep His devotee’s promise, the Lord broke His own promise.