After Howard Kirby bought a footstool from a charity shop in the US state of Michigan, he felt the cushion "seemed kind of hard".

It had been purchased around Christmas along with other furniture from a fundraiser shop for the charity Habitat for Humanity for just US$70 ($102).

When his daughter-in-law unzipped the footstool's cushion, there was $43,170 ($62,000) stashed inside.

After the shock wore off, Mr Kirby decided to return the money to the original owners — the family of Kim Fauth-Newberry.

"I do what I can to be as much like Christ as I can, and this is the moral thing to do," Mr Kirby, 54, said.

"This is going to help them. I'm so happy for them."

Ms Fauth-Newberry said the furniture had belonged to her grandfather, Phillip Fauth, who died in July.

She said Mr Fauth was a frugal man who always paid for things in cash, even US$9,000 ($13,000) for a new roof.

The newly discovered money was separated with paper clips and topped with handwritten notes.

"To me, this is someone that despite what they're going through — and in spite of their own needs — says 'I'm just going to do the right thing'," said Rick Merling, the manager of the op shop, as quoted by local media.

ABC/AP