The voice of Jesus explained to David—because it instructed the apostles 2,000 a long time before, “Freely you may have been given; freely give.” Hence David hasn't charged for his time, training or any of the many products he gives away, but has actually been supported solely by appreciate offerings. https://www.youtube.com/playlist?list=PLXR6KmNsDBjSQgdIOJ1JFzHP8923tHwyl