This can be stated in active form. AT: "that Yahweh may cause you and your children to live a long time" (See: [[rc://en/ta/man/translate/figs-activepassive]])
This compares how long the people could stay in the land to how long the sky will exist above the earth. This is a way of saying "forever." AT: "to give them as a possession forever" or "to allow them to live there forever" (See: [[rc://en/ta/man/translate/figs-simile]])