Where I live - in Jerusalem - it's not uncommon to see signs like this:
I said Perek Shira for 40 days and was saved. I promised to publicize this.
Sometimes it's about other good deeds, usually it's about Perek Shira. (See here for the origins of Perek Shira.)
Essentially, the person says (to himself and Hashem) "I will say Perek Shira for 40 days so that in the merit of doing so I will get engaged/cured/whatever is bothering me and if my prayers are answered I will publicize this".
Where does this concept come from of promising to publically publicize one's redemption - and how it was done - if one is redeemed after doing something?
Any ideas, hints, stories and even sources are welcome.
(I think the concept of publicising a redemption per se can be easily sourced.)