with your blessing your servant's house will be blessed forever

This can be stated in active form. Alternate translation: "you will continue to bless my family forever" (See: rc://en/ta/man/jit/figs-activepassive)

your servant's house

Here David refers to himself as "your servant." Alternate translation: "my house" or "my family" (See: rc://en/ta/man/jit/figs-123person)