At the age of 35 he united with the Church of the Brethren and was from the start an earnest student of the Bible. He could read German and English equally well, had a wonderful memory, and soon had a storehouse of biblical knowledge that was a great help to him all through life. Where Jacob and his bride Mary located there was no churchhouse; neither was there any minister. In 1835 the Sandy Creek congregation was organized and a year later Jacob was called to the ministry. Under his leadership the congregation increased rapidly and soon a large house, named Salem, was erected. This was much enjoyed by a people who had been holding their meetings and love feasts in barns and homes under many discomforts.
Jacob did not limit his ministry to the local congregation but would travel astride his horse over a large territory of Pennsylvania, West Virginia, and even into Maryland. Sometimes he was gone for four months at a time. By requests of judges and lawyers he preached in the courthouses of three counties. All this was done without compensation but he lived to see his labors bear fruit in multiplied congregations.
When he was in his mid-70s he became very sick and the attending physician told him one morning that his end was at hand, and left, telling his neighbors that Brother Thomas was dying. But not so. He called for the anointing, recovery speedily followed, and the doctor, who said he had felt a death pulse in him, was amazed.
Source: Some who led, as told by Bishop Jeremiah Thomas