I find this video quite beneficial, especially for those who do dawah. Even if the disbelievers deny the truth, etc. They will testify for you, that indeed, they heard you preaching the message.

And even if the disbeliever denies, there might be a Jinn who submitted / converted to Islam by your dawah. Even reciting the adhan, every stone, believer, disbeliever, who heard you, will testify to Allah, that indeed, they heard. according to this video.

https://www.youtube.com/watch?v=jy5VJtqSEAU

And may Allah forgive me if I said anything wrong. Ameen.

And Allah knows best.