He gained great influence, and was nicknamed the ‘bishop of Shropshire.’ In 1654 he was made assistant to the commissioners for ejecting insufficient ministers in Shropshire, Middlesex, and Westminster.
Anthony Wood calls him ‘the common epitaph-maker for dissenters;’ Calamy says he wrote but three, for Thomas Goodwin, D.D., John Owen, D.D., and Ichabod Chauncey.
He was on intimate terms with Hall, Ralph Bathurst, master of Trinity, Aldrich, Wallis, and Jane.
Calamy describes him as ‘very purblind,’ as ‘the completest schoolman’ he ever knew, in his element among ‘crabbed writers,’ yet sometimes ‘very facetious and pleasant in conversation.’ Calamy has preserved some of his stories, told after a supper of ‘buttered onions.’ Gilbert died at Oxford on 15 July 1694, and was buried in the chancel of St Aldate's Church.
A Learned and Accurate Discourse concerning the Guilt of Sin, 1695, though Calamy speaks as if it had been first printed in Gilbert's lifetime.
He had a hand in the Annus Mirabilis for 1661 and following years, and wrote the largest part of a Latin version (Amsterdam, 1677) of Francis Potter's Interpretation of the Number 666 Oxford, 1642.