Walter Wilson, following Josiah Thompson, thinks he was educated at Timothy Jollie's Attercliffe Academy, near Sheffield (opened in 1689).
Records of the presbyterian board show that in 1692–1696 he studied successively in the academies of John Southwell at Newbury, Berkshire, and James Waters at Uxbridge, Middlesex.
He began early to preach, and was some time assistant (unordained) to Henry Read at Gravel Lane, Southwark.
On Read's death (1698) Harris was called to succeed Timothy Cruso at Crutched Friars, in spite of some opposition, and received presbyterian ordination.
Harris died, following a short illness, on 25 May 1740, and was buried (in 30 May) in Daniel Williams's vault at Bunhill Fields burial ground.