He was born at Auchtermuchty, Fife, where his father was parish minister. He was educated at Kinclaven and the grammar school, Perth, graduated from the University of St Andrews in 1713, and completed his education for the ministry at Edinburgh. He was licensed as a preacher by the presbytery of Dunkeld, and soon afterwards ordained by that of Dundee as minister of the parish of Tealing (1719), where his preaching soon drew a large congregation. Early in his ministry he was brought to a halt while lecturing on the Shorter Catechism by the question "How doth Christ execute the office of a king?" This led to an examination of the New Testament foundation of the Christian Church, and in 1725, in a letter to Francis Archibald, minister of Guthrie, Forfarshire, he repudiated the obligation of national covenants.
In the same year he formed a society separate from the multitude, numbering nearly a hundred, and drawn from his own and neighbouring parishes. The members of this ecclesiola in ecclesia pledged themselves to join together in the Christian profession, to follow Christ the Lord as the righteousness of his people, to walk together in brotherly love, and in the duties of it, in subjection to Glas as their overseer in the Lord, to observe the Lord's Supper once a month and to submit themselves to the Lord's law for removing offences. From the scriptural doctrine of the essentially spiritual nature of the kingdom of Christ, Glas in his public teaching drew the conclusions:
For these opinions he was in 1728 suspended from his ministerial functions, and finally deposed in 1730. The members of the society already referred to, however, for the most part continued to adhere to him, thus constituting the first Glassite or Glasite church. The seat of this congregation was shortly afterwards transferred to Dundee (whence Glas subsequently removed to Edinburgh), where he officiated for some time as an elder. He next labored in Perth for a few years, where he was joined by Robert Sandeman, who became his son-in-law, and eventually was recognized as the leader and principal exponent of Glas's views; these he developed in a direction which laid them open to the charge of antinomianism.
Ultimately in 1730 Glas returned to Dundee for the remainder of his life. He introduced in his church the primitive custom of the osculum pacis and the agape celebrated as a common meal with broth. From this custom his congregation was known as the kail kirk. In 1739 the General Assembly, without any appeal from him, removed the sentence of deposition against him, and restored him to the status of a minister of the gospel of Christ, but not that of a minister of the Established Church of Scotland, declaring that he was not eligible for a charge until he should have renounced principles inconsistent with the constitution of the church.
Glas's published works bear witness to his vigorous mind and scholarly attainments. His reconstruction of the True Discourse ef Celsus (1753), from Origen's reply to it, is a competent and learned piece of work. The Testimony of the King of Martyrs concerning His Kingdom (1729) is a classic repudiation of erastianism and defence of the spiritual autonomy of the church under Jesus Christ. His common sense appears in his rejection of John Hutchinson's attempt to prove that the Bible supplies a complete system of physical science, and his shrewdness in his Notes on Scripture Texts (1747). He published a volume of Christian Songs (Perth, 1784). A collected edition of his works was published at Edinburgh in 1761 (4 vols., 8vo), and again at Perth in 1782 (5 vols., 8vo).
Reference