[3] He preached in the Greyfriars church on 28 February 1638, when the National Covenant was signed, and presided as Moderator of the memorable General Assembly held at Glasgow in the following November.

Henderson was entrusted with various important missions; he was one of the commissioners who represented the Scottish Church at the Assembly of Divines at Westminster, and he was honoured with several interviews by Charles I when he endeavoured, though unsuccessfully, to bring the king over to Presbyterianism.

Robert Bruce's sermon made such a powerful impression upon him that it effected an entire change in his religious conduct and sentiments; and from being a careless and indifferent pastor over his flock, and an upholder of a system odious in the highest degree to the people, he became a watchful and earnest minister, and a resolute champion in the cause of Presbyterianism.

[4] Henderson stood among the foremost of those who opposed, though unsuccessfully, the obnoxious measure; and this too, in defiance of the king's utmost wrath, with which all who resisted the adoption of the Five articles were threatened.

"In case of your refusal," said the archbishop of St Andrews, addressing the assembled clergymen, "the whole order and estate of your church will be overthrown, some ministers will be banished, others will be deprived of their stipends and office, and all will be brought under the wrath of authority."

[4] With the memorable year 1637 Henderson reappears on the scene, a keen opponent of the Scottish Prayer Book, also known as "Laud's Liturgy," which King Charles was determined to foist on the Church.

He immediately went to Edinburgh, and, 23 August, presented a petition to the privy council, representing that the service book had not received the sanction of the General Assembly, nor was recognised by an act of parliament, and praying a suspension of the charge.

A great number of the nobility, gentry, clergymen, and representatives of burghs, with others, had assembled in Edinburgh from all parts of the country; and after another supplication had been presented to the privy council, praying them to bring the matter again before the king, a proclamation from his majesty was made, requiring all persons to depart to their homes within twenty-four hours, on pain of being denounced rebels.

Instead of dispersing, the leaders of the popular party, after some farther ineffectual petitions to the king, resolved to appeal to the people, and the result was the renewal of the National Covenant of 1580 and 1581, with only some slight changes adapted to the circumstances of the times.

It was prepared by Mr. Henderson, assisted by Lord Warrison, Archibald Johnston, an advocate in whom, we are told, the suppliants chiefly confided, and was sworn and subscribed in the Greyfriars' church of Edinburgh, on 28 February 1638, by thousands of the nobility, gentry, ministers of the gospel, burgesses, and others.

He was subsequently sent with several noblemen, and Messrs. Cant and Dickson, to Aberdeen, to prevail on the inhabitants of that city to take the Covenant, and, after urging upon them the strongest arguments in favour of the document, no less than 500 persons subscribed it, many of them being of the highest respectability.

Henderson was mainly responsible for the final form of this document, which consisted of: Owing to the skill shown on this occasion he seems to have been applied to when any manifesto of unusual ability was required.

[7] While Scotland and England were preparing for the First Bishops' War, Henderson drew up two papers, entitled respectively The Remonstrance of the Nobility[11] and Instructions for Defensive Arms.

[7] At the memorable General Assembly which met at Glasgow the same year, 21 November 1638, the first that had been held for a long period, Mr. Henderson, now the acknowledged leader of the clergy, was unanimously chosen moderator.

After the deposition and excommunication of the bishops, and the formal abolition of Episcopacy, Mr. Henderson terminated the proceedings with an eloquent and impressive address to the members of the Assembly, concluding with these striking words: — "We have now cast down the walls of Jericho; let him that re-buildeth them beware of the curse of Hiel the Bethelite!

[16] In 1639 he was one of the commissioners appointed by the Church to treat regarding the articles of pacification with the king; and during the whole of the difficult negotiations that ensued, he behaved with great prudence and candour.

On the 31st of the same month, he was called upon to preach at the opening of parliament, on which occasion he delivered an excellent discourse, in which he treated, with consummate ability, of the end, duties, and utility of magistrates.

The king having refused to ratify some of the points agreed upon at the late pacification, suddenly prorogued the parliament, denounced the Covenanters as rebels, and prepared again to invade Scotland.

[15] But the successes of the Scots army, which entered England in August 1640, compelled him to accede to another proposition for peace; and a conference was begun at Rippon, which, in a short time after, was transferred to London.

[17] Before he left London he was admitted to a private conference with the king, the special object of which was to procure assistance to the Scottish universities from the rents formerly appropriated to the bishops, when he was graciously received by his majesty.

[18][19] In 1640 the town council of Edinburgh, with the view of rendering the system of education at the university more efficient, resolved to appoint annually a rector of that institution, and unanimously elected Mr. Henderson to the situation.

[17] In this Assembly he proposed that a confession of faith, a catechism, a directory for all the parts of the public worship, and a platform of government wherein possibly England and we might agree, should be drawn up.

During Charles's second state visit to Scotland in the autumn of 1641, Henderson acted as his chaplain and managed to get the funds, formerly belonging to the bishopric of Edinburgh, applied to the metropolitan university.

The Assembly unanimously approved of a motion which he brought forward, to the effect that they should take steps for drawing up a Confession of Faith, Catechism, Directory of Worship, and Form of Government; and remitted to him to prepare the necessary drafts of these documents.

On 14 August, the king arrived at Edinburgh to be present at the parliament; on which occasion, wishing to conciliate the presbyterian party, he appointed Mr. Henderson his chaplain.

[21] During the year 1642, the time of the English Civil War, Henderson was employed in managing the correspondence with England respecting ecclesiastical reformation and union.

Anxious to effect a reconciliation between Charles and his English subjects, he joined with some other leading men in an invitation to the queen to come to Scotland; but this proposition was rejected by the king.

Accompanied by the other commissioners, he next went to Oxford, where his majesty then was, to offer him the mediation of Scotland; but the infatuated monarch, instead of making some concessions for the sake of peace, endeavoured to convince him of the justice of his cause, defended all his proceedings, and expressed his high indignation at the interest which the Scots took in the reformation of the church in England.

"[17] In 1643 he was, for the third time, chosen moderator of the General Assembly — an occasion which was rendered remarkable by the presence of the English commissioners sent down by the parliament to crave their aid and connsel in the then critical circumstances of both kingdoms.

During the three following years he remained in London, unremittingly engaged in assisting the Westminster Assembly in preparing the public formularies for the religious union between the three kingdoms.