This refers to God's rule as king. The phrase "kingdom of heaven" is used only in the book of Matthew. If possible, use "heaven" in your translation. (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here "bind" is a metaphor meaning to forbid something, and "loose" is a metaphor meaning to allow something. Also, "in heaven" is a metonym that represents God himself. Alternate translation: "God in heaven will approve whenever you forbid or allow something on earth" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-metonymy]])