In the 1680s Jacobi attended the University of Halle, one of the main centres of Lutheranism, where the leading Pietist August Hermann Francke set up various educational institutions.
He specialised in religious tracts, using his contacts with Francke in Halle and John Downing of the Society for Promoting Christian Knowledge in London.
He produced several English translations including Estrid: An Account of a Swedish Maid, who hath Lived Six Years without Food (1711).
In 1714 he was appointed "chapel-keeper" (or verger) of the Royal German Chapel, St James's Palace, which provided Lutheran services for the Hanoverian court.
Later that year—inspired by Nitschmann but discouraged by Friedrich Michael Ziegenhagen, Boehm's successor at the Royal German Chapel in 1722—Jacobi, accompanied by his three daughters, made the journey to Herrnhut in Saxony, where the original Moravian movement had been offered protection.