He held a prominent place in the New School branch of the Presbyterians, to which he adhered on the division of the denomination in 1837; he had been tried (but not convicted) for heresy in 1836, the charge being particularly against the views expressed by him in Notes on Romans (1835) of the imputation of the sin of Adam, original sin and the atonement; the bitterness stirred up by this trial contributed towards widening the breach between the conservative and the progressive elements in the church. He was an eloquent preacher, but his reputation rests chiefly on his expository works, which are said to have had a larger circulation both in Europe and America than any others of their class.
Of the well-known Notes on the New Testament it is said that more than a million volumes had been issued by 1870. The Notes on Job, the Psalms, Isaiah and Daniel, found scarcely less acceptance. Displaying no original critical power, their chief merit lies in the fact that they bring in a popular (but not always accurate) form the results of the criticism of others within the reach of general readers. Barnes was the author of several other works of a practical and devotional kind, and a collection of his Theological Works was published in Philadelphia in 1875. He died in Philadelphia on the 24th of December 1870.