Ariana Grande gave one New York City Marathon finisher a memory she will never forget. The pop star did it with a pen and a few kind words.

Ari and her boyfriend Ricky Alvarez were out on the sidelines Sunday cheering for the thousands of people pounding the pavement. That is when influencer Ella Schweiger walked up with an unusual ask.

Ella wanted the couple to write an encouraging message for someone they had never met who had just finished all 26.2 miles.

"You did it!"

Ariana happily agreed. She wrote "You did it!" on the card and decorated it with hearts. She signed it "Ari + Ricky."

Ella later posted a clip on Instagram. It shows her approaching the pair and then handing the card to a runner named Ellie, who could hardly believe who had written it.

Ellie had a surprise of her own. She said she had been playing Ariana's songs while she ran and that one track carried her through a tough patch near mile 24.

Spreading kindness one card at a time

The moment was part of a project Ella calls "Ella's Envelope." She gathers upbeat notes from strangers and passes them along to runners as a reminder that small gestures matter.

Ariana and Ricky got back together earlier this year almost ten years after they first split. They went public on Instagram in August.