Answer by Harini Pandiyan
"Stay blessed" signifies "May you stay in God's favor."
In older English, it was worded as "May God never turn his face from you." Stay blessed is more imperative when a speaker wants to express to the person he is speaking to – Is doing good (behavior).
Stay blessed is usually addressed with religious beliefs in mind; it can also be a generic phrase. If you say this phrase to someone, you denote that you would like them to continue having good things in their life.