Reuben was born on November 17, 1973, to Emmanuel and Fannie Mast. He grew up in the Amish community and married Freda in 1997. Married for nearly 20 years, Reuben and Freda were blessed with three children, David Mast, Diane Mast, and Darlene Mast.

Reuben was a loving, big-hearted man whose main focus in life was God and his family. Without hesitation, he would always be there to help someone. He joined the Wayne Township Volunteer Fire Department to do exactly that, to help anyone he could. As a day job, Reuben drove a semi-truck, something else he enjoyed immensely. He would often participate in local parades, waiting for a chance to show off his shined-up rig. Reuben was also a member at Light in the Valley Chapel in Walnut Creek, Ohio.

On the day of his death, December 19, 2016, Reuben was responding to an ambulance call when he lost control of his truck and crashed into the guardrails.

He is dearly missed by everyone—his fellow firefighters, church family, friends, and most of all his family.