how to be rewarded by God openly

The Handed down, Received, Preserved word of God has the word "openly" unlike the Critical Text.

Don't get caught up in fleshly guilt-milking sermons. Because, why would God incentivize you, and then slap your hand for "bad motivations" which He motivated you with?

Also, if you want to be productive at all, it requires success, and success glorifies. Glorify God privately, and receive His open reward. (And don't forget to glorify Him with hard work.)