SB 1.8 - Yudhiṣṭhira feels responsible for the war
The King felt he was most sinful and said that the body, which was ultimately meant for others, had killed many, many phalanxes of men. A solid phalanx of 21870 chariots, 21870 elephants, 109,650 infantry and 65,600 cavalry is called an akṣauhiṇī. While there is life it is meant for the service of others, and when it is dead it is meant to be eaten by dogs and jackals. Yudhiṣṭhira felt hell awaited him for all sins committed by killing many boys, brāhmaṇas, well wishers, friends, parents, preceptors and brothers. There is no sin for a king who kills for the right cause, who is engaged in maintaining his citizens, but Yudhiṣṭhira felt this injunction did it apply to him. He felt he had caused all the killing only for his personal gain of the kingdom from Duryodhana, who was ably ruling the kingdom. The killing was done not in the course of administration but for self aggrandizement, and as such Yudhiṣṭhira thought himself responsible for all the sins.
Yudhiṣṭhira said he had killed many friends of women, and had thus caused enmity to such an extent that it was not possible to undo it by material welfare work. Most people do welfare work for the sake of material prosperity. Such prosperity is sometimes hampered by sinful activities, for the materialist is sure to commit sins, even unintentionally, in the course of discharging duties. The Vedas prescribe several sacrifices like the Aśvamedha-yajña to get relief from sinful reactions. Yudhiṣṭhira felt it was not possible to get relief from his sins even by performing yajñas. When people are killed, a fresh enmity is created with the surviving relatives and thus a chain of actions and reactions is set in. The way of work is like that. Karma binds one by creating actions and reactions, and only by working on behalf of the Supreme can one be free from material bondage. Factually no sin touched the Pāṇḍavas, who were only the order carriers of the Lord.
Yudhiṣṭhira felt that it was not possible to counteract the sins of killing men by sacrificing animals just as it is not possible to filter muddy water thru mud or purify a wine-stained pot with wine. Horse and cow sacrifices were not for the purpose of killing animals, for the sacrificed animals get a new life. The sacrifice was meant to prove the efficacy of the hymns of the Vedas. By proper conduct of sacrifice, the performer gets relief from sins and the animals are also rejuvenated. In Kali yuga there are no expert brāhmaṇas to conduct such yajñas and so the only sacrifice recommended is the hari-nāma yajña. The whole purpose of life is to serve the will of the Lord.