As has been already mentioned, the exclusive authority of the Book of Common Order, as a guide and aid to ministers in conducting public worship and administering the sacraments, was asserted by the General Assembly in 1564. It continued to hold the place thus given to it down to 1637, when it was superseded, in so far as the king and his council were concerned, first, by what is known as Archbishop Laud's Liturgy, and then by an injunction of the disappointed prelates, which required that, till further order should be taken, neither the new nor the old liturgy should be used in the public services, in Edinburgh, but only those prayers which the ministers had been accustomed to make before and after their sermons.[161] Thus the bishops themselves were the unwitting instruments of first setting aside a partially liturgic, and introducing instead a wholly extemporary, form of worship into Scotland. There is no reason, however, for maintaining that the Book of Common Order, while it continued in authority, was regarded as more than a guide or model, at least to the ordained ministers, or can be so regarded by any one who studies with care its rubrics and general contents, far less was observed as a rigid liturgy, every word of which must be repeated unvaryingly by the officiating minister. It has indeed been maintained, even in recent times, and by ministers of the National Church, that "the idea of extemporaneous prayer as an appropriate vehicle of public devotion was one quite unknown to the Reformation." But this cannot be made good with respect to any of the Reformed or Calvinistic churches, and certainly least of all with respect to the National Church of Scotland at any period of its history. Our reformers laid it down in their First Book of Discipline as a fixed principle that "it is neither the clipping of their crownes, the greasing of their fingers,[162] nor the blowing of the dumb dogges called the bishops, neither the laying on of their hands, that maketh true ministers of Christ Jesus. But the Spirit of God, inwardly first moving the heart to seeke to enter in the holy calling for Christ's glory and the profite of His Kirk, and thereafter the nomination of the people, the examination of the learned, and publick admission, ... make men lawfull ministers."[163] They distinctly taught that no one was to be regarded as a lawful minister of Christ into whose mouth Christ had not put _some word of exhortation_ or vouchsafed some gift of expounding and preaching the Word of God,[164] and they expressly encouraged their ministers to look for their Master's aid and guidance in praying as well as in preaching. Hence throughout their Book of Common Order they carefully abstained from imposing the _ipsissima verba_ of particular forms as rigidly binding, or even from encouraging their ministers to rest contented with the stated repetition of them. [Sidenote: Its tolerant Rubrics.] [Sidenote: Calderwood's Testimony.]