“H ashem should do with you chesed like you did with the dead ones and with me.” (Megillas Ruth 1:8)
Rav Zeira says (Yalkut Shemoni 147): “This megillah doesn’t teach us [laws of] impurity or purity what is permitted and what’s forbidden. So why was it written? To teach you the reward of those who do chesed.”
When reading Megillas Ruth one cannot help but notice the incredible levels of emunah and bitachon Ruth had. She gave up wealth and royalty to tie her future to a poor old woman whose livelihood would come from collecting stalks in the field.
There’s no doubt that this nisayon highlights Ruth’s incredible levels of faith.