A note found inside a book in a Target store in Missouri just set off a chain reaction of random acts of kindness that has touched the hearts of people all over the world.

It all started when 27 year-old Ashley Jost was shopping at the Target and came upon a self-help book called “Girl, Stop Apologizing.” Ashley bought the book and started reading it as soon as she got home, but after a few minutes, her dog started barking and she tossed the book aside. When she returned, Ashley was stunned to see that something had fallen out of the book onto the ground.

“Five dollars fell out, and it took me a second where I was like, ‘Wait, what just happened?'” Ashley recounted. After flipping through the book, Ashley found a Post-it note that read:

“To the person who buys this book: I am having a tough day. I thought maybe I could brighten someone else’s with this little surprise. Go buy a coffee, a donut or a face mask. Practice some self care today. Remember that you are loved, you are amazing, you are strong. – Lisa”

Ashley posted a photo of the note and money on Twitter, where it quickly went viral. Since then, social media users all over the world have been pledging to pay it forward by performing their own acts of kindness.

“In that moment, I didn’t necessarily need the pick-me-up, but I feel obligated to share it, and I’m hearing back from people who did,” Ashley said. “The ripple effect is pretty incredible.”

Eventually, Lisa (the author of the note) came upon the post and sent Ashley a card.

“She said it made her cry in a good way,” Ashley said, adding that Lisa did not reveal her full name, as she prefers to remain anonymous. Ashley also said that Lisa had also told her that she had been going through a difficult time in her life and wanted “to create something positive — she never really expected this to happen the way it has.”