After Samuel Davies completed his studies with Blair, the Presbytery of New Castle licensed him to preach in 1746. He joined the New Side synod of New York, and married Sarah Kirkpatrick on October 23, 1746, while he was preaching in Pennsylvania and Delaware. Commissioned as an evangelist to Virginia several months later, on February 17, 1747, the 23 year old traveled south to minister to religious dissenters against the Anglican Church. Virginia’s colonial legislature in 1743 had licensed Polegreen reading room and three others in and near Hanover County, Virginia. Davies eventually led seven congregations in five counties, fulfilling his duties despite frail health from tuberculosis. His beloved wife Sarah also died from a miscarriage on September 15, 1747, shortly before their first anniversary. Her death led Davies to believe that he too was near death, and he therefore threw himself wholeheartedly into his preaching ministry. Samuel Davies eventually recovered his health, but continued to preach enthusiastically and very well. Young Patrick Henry attended many of Davies’ sermons with his mother and acknowledged that at the source of his own oratorical skills; others called Davies without peer in the pulpit during his lifetime. Davies returned to Virginia in May 1748, and on October 4, 1748, married Jane Holt, from a prominent Williamsburg family. He fathered six children with Jane, including one child who died at birth.

As one of the first non-Anglican ministers licensed to preach in Virginia (with the now-dead Francis Makemie), Samuel Davies advanced the cause of religious and civil liberty in his era. Davies’ strong religious convictions led him to value the “freeborn mind” and the inalienable “liberty of conscience” that the established Anglican Church in Virginia often failed to respect. Davies helped found the Presbytery of Hanover, encompassing all Presbyterian ministers in Virginia and North Carolina. He served as its first moderator and was considered the region’s leading voice for religious dissenters. By appealing to British law and notions of British liberty, Davies agitated in an agreeable and effective manner for greater religious tolerance and laid the groundwork for the ultimate separation of church and state in Virginia that was consummated after his departure by the Virginia Declaration of Rights in 1776 and the Statute for Religious Freedom in 1786. Rev. Davies also served as the first minister at Providence Presbyterian Church in Louisa County, Virginia until his departure for New Jersey in 1759.

While in Virginia, unlike the earlier Rev. Makemie, Samuel Davies advocated educating slaves, including teaching them to read. Unlike Baptist and Methodist evangelists, who based conversion solely on an outpouring of the spirit, Davies believed that no one, regardless of race or social status, can have true religion without both hearing and reading the Word of God. Although personally not opposed to slavery, Davies believed that slaves deserved direct access to the word of God the same as their masters. Slaves became a particular focus of his ministry, and several contemporaries noted how Davies converted African slaves at unusually high numbers. Davies used the educational materials he received from his sponsors in Great Britain to instruct slaves, as well as composed his own hymns. The classic spiritual “Lord, I want to be a Christian in my heart” reportedly originated at Polegreen. Rev. Davies eventually baptized hundreds as Christians, and they joined other members of the congregation at the communion table. His congregations allowed slaves to preach in the Church. Davies estimated that he ministered to over a thousand black people during his time in Virginia.

As Samuel Davies began his ministry in Virginia, six students began studies in Elizabeth, N.J., at the College of New Jersey, which had been established in 1746 to educate “those of every Religious Denomination.” In 1753 the college’s trustees persuaded Davies, famed for his work in Virginia, to make the dangerous voyage to Great Britain to raise money for the fledgling school. Davies confided the sometimes harrowing journey to his diary, as well as noted “To be instrumental of laying a foundation of extensive benefit to mankind, not only in the present but in future generations, is a most animating prospect.” Rev. Davies and a fellow Presbyterian minister, Gilbert Tennent spent eleven months in Great Britain, with Davies preaching sixty times. The two raised substantial sums, mainly through church collections. The grandson of Oliver Cromwell gave three guineas to support their efforts. Davies and Tennent eventually raised a total of four thousand pounds on behalf of the College of New Jersey, enough to build Nassau Hall as the first permanent building on the new campus in Princeton. After his return from Great Britain, Davies’s prominence in Virginia grew during the French and Indian War. Governor Dinwiddie declared Davies to be the colony’s best recruiter, as he implored men to do their part “to secure the inestimable blessings of liberty.”. In 1759, four years after Davies returned from his British fundraising tour, the College’s trustees called on him again, this time asking him to become the school’s fourth president. Davies initially declined the position, thinking that trustee Samuel Finley was better qualified. Eventually Davies accepted the job, and succeeded Jonathan Edwards, who had died just six weeks after his inauguration.

Samuel Davies’s own term as president also proved short — he died in 1761 at the age of 37. His final published sermon was eerily entitled “This Very Year You Shall Die!” and delivered at Princeton on New Year’s Day, 1761. Davies preached using Jeremiah 28:16 as his reference text, proclaiming that “it is not only possible–but highly probable, that death may meet some of us within the compass of this year.” Almost prophetically, Davies died one month later from pneumonia, on February 4, 1761. Rev. Finley succeeded him as the school’s president, and Davies was buried alongside his predecessor in Princeton Cemetery.