BG Chap 11 - Being an instrument to the Lord's will (nimitta mātraṁ)
Kṛṣṇa urged Arjuna to rise, fight and win glory. Conquering the enemies, Arjuna would enjoy a prosperous kingdom. Kṛṣṇa asks Arjuna to just be His instrument because Arjuna’s enemies had already been killed by Kṛṣṇa’s arrangement. Warriors such as Bhīṣma, who could not be conquered even by the devas, would be easily defeated by Arjuna. They had already been killed by Kṛṣṇa at the time of their offending Draupadī. They were proceeding like puppets to give Arjuna fame. Kṛṣṇa encourages Arjuna to use all his skills to fight, by addressing him as Savya-sācin, which means one who can fight with either left or right hand, and slay Droṇa, Bhīṣma, Karṇa, Jayadratha and other brave warriors, who were already put to death by Kṛṣṇa. Jayadratha was given a boon by Lord Śiva that he would be able to stop the Pāṇḍavas once. Kṛṣṇa assures Arjuna that Arjuna would be victorious over all his enemies.
The whole world is moving according to the plan of the Supreme Personality of Godhead. Foolish persons who do not have sufficient knowledge think that nature is moving without a plan and all manifestations are but accidental formations. But there is a specific plan being carried out in this material world. This cosmic manifestation is a chance for the conditioned souls to go back to Godhead, back to home. As long as they have the domineering mentality which makes them try to lord it over material nature, they are conditioned. But anyone who can understand the plan of the Supreme Lord and cultivate Kṛṣṇa consciousness is most intelligent. The creation and destruction of the cosmic manifestation are under the superior guidance of God. Thus the Battle of Kurukṣetra was fought according to the plan of God. Arjuna was refusing to fight, but he was told that he should fight in accordance with the desire of the Supreme Lord. Then he would be happy. If one is in full Kṛṣṇa consciousness and his life is devoted to the Lord's transcendental service, he is perfect.