What does it mean to be sealed with the Holy Spirit of promise?
It means that after believing, God marks the believer as His own by the indwelling Holy Spirit of promise, not by church membership or baptism. That seal is His brand of ownership and the earnest, or down payment, of the believer's inheritance.
Les explains that salvation is not obtained through church membership or baptism—whether sprinkling, pouring, or immersion—because those things are not the basis of salvation. After a person believes, God seals and brands them. Using the illustration of a cowman and a brand that marks ownership, Les teaches that the indwelling Holy Spirit is God's mark of ownership for the believer. Being sealed with that Holy Spirit of promise is the earnest, or down payment, of our inheritance.