Mbh 7.79.1b

Oh, let Arjuna succeed in fulfilling his vow. Difficult is that vow which he, afflicted with grief on account of his son, hath made. Duryodhana’s brothers are all possessed of great prowess. His forces also are countless. The son of Dhritarashtra hath assigned all these to Jayadratha (as his protectors). Oh, let Dhananjaya come back (to the camp), having slain the ruler of the Sindhus in battle. Vanquishing his foes, let Arjuna accomplish his vow. If he fails to slay the ruler of the Sindhus tomorrow, he will certainly enter into blazing fire. Dhananjaya, the son of Pritha, will not falsify his oath. If Arjuna dies, how will the son of Dharma succeed in recovering his kingdom? Indeed, (Yudhishthira) the son of Pandu hath reposed (all his hopes of) victory of Arjuna. If we have achieved any (religious) merit, if we have ever poured libations of clarified butter into fire, let Savyasachin, aided by the fruits thereof, vanquish all his foes.” Thus talking, O lord, with one another about the victory (of the morrow), that long night, O king, of theirs, at last, passed away. In the middle of the night, Janardana, having awaked, remembered Partha’s vow, and addressing (his charioteer) Daruka, said, “Arjuna, in grief for the death of his son, hath vowed, O Daruka, that before tomorrow’s sun goes down he will slay Jayadratha. Hearing of this, Duryodhana will assuredly take counsel with his counsellors, about how Partha may fail to achieve his object. His several Akshauhinis of troops will protect Jayadratha. Fully conversant with the ways of applying all weapons, Drona also, with his son, will protect him. That matchless hero, the Thousand-eyed (Indra himself), that crusher of the pride of Daityas and Danavas cannot venture to slay him in battle who is protected by Drona. I, therefore, will do that tomorrow by which Arjuna, the son of Kunti, may slay Jayadratha before the sun sets. My wives, my kinsmen, my relatives, none amongst these is dearer to me than Arjuna.