Webster was a Scottish Covenanter who was imprisoned for his faith. After the killing times were over, he was ordained to the gospel ministry in the Church of Scotland, and served two country parishes in the Lothians before being inducted as pastor of one of the Edinburgh congregations in 1693. He initiated the prosecution of Professor John Simson, whose teaching inclined to Arianism. As well as the two published volumes of his sermons, Webster wrote a defence of Presbyterian church government, and two expositions of covenant theology.