He returned to England under the Commonwealth, went to Scotland after a period at Oxford, and became a Fellow of Trinity College, Dublin.
[1] Having already become a preacher, Mather returned to England, and in 1650 was made one of the chaplains of Magdalen College, Oxford, under the presidency of Thomas Goodwin, the Independent.
[1] In 1653 Mather resigned his chaplaincy, having been appointed to attend the parliamentary commissioners who journeyed to Scotland to proclaim and implement the Tender of Union.
On 5 December 1656 he was ordained in the Church of St. Nicholas Within,[1][3] Dublin, by Samuel Winter, provost of Trinity, Timothy Taylor of Carrickfergus, and Thomas Jenner (born 1606/7) of Drogheda, all Independents.
Wood commends him for his civility to episcopal divines; he declined to act on commissions for displacing them in Munster and Dublin.
Crossing to England he obtained the perpetual curacy of Burtonwood, Lancashire, a poor chapelry with a wooden chapel, in the parish of Warrington.
He went back to Dublin and gathered a congregation, which met at his house till a meeting-house was erected in New Row.