The third petition of the Lord's Prayer, "Your will be done, on earth as it is in heaven," relates to the second petition, "Your kingdom come," in that it extends it.
In the second petition, the request for God's kingdom to come can be understood as a plea for God's reign and authority to be established on Earth. The third petition further elaborates on how that reign is manifested: by doing God’s will on Earth as it is perfectly done in heaven. Therefore, while the second petition seeks the coming of God's kingdom, the third petition expresses the desire for the conditions of that kingdom—specifically, the fulfillment of God's will—to be realized in the world. Together, they emphasize the holistic vision of God's rule and purpose being accomplished in both the spiritual and earthly realms.