Witsius writes (not an endorsement or promotion of Witsius as a true Christian; paragraphing mine):
“It is necessary, however, to take heed that we associate only with a true Church lest we embrace a prostitute and an adulteress, instead of the chaste Spouse of Christ. Amidst so great a multitude of societies which vie with each other in claiming to themselves the name of the Church, it appears an arduous task for a man concerned for the salvation of his soul to determine which of them ought to be preferred. But there is in particular one characteristic by which, without great difficulty, you may discriminate the true Church of Christ from an adulteress, to wit, the truth of the heavenly doctrine.
If a society devoutly profess the truth as it was delivered by Christ, and by the Prophets and Apostles, you may safely recognise it…whether considered individually or collectively…we profess that there has existed from the beginning of time, still exists, and will continue to the end of the world to exist, a society of men chosen by God to salvation, called by the Gospel and the Spirit, professing faith and piety with the mouth, and practising them in the conduct.
We declare also, that neither the machinations of the world that lieth in wickedness, nor the gates of hell, shall ever prevail against this society. For it is utterly impossible that the decree of God should fail; that the promises of God should come to nought; that the word of salvation should be preached in vain; that the prophecies respecting the perpetuity of Christ’s kingdom should fall to the ground; or that Christ should lose the reward of his labour and become a Master without disciples, a King without subjects, a Bridegroom without a bride, a Head without a body.
Nor is it sufficient to believe and profess this in general. We must endeavour in our meditations to enter more deeply into the subject that we may adore with reverence and with a sort of holy amazement, the methods of God’s procedure in the government of the Church and the displays which it affords of His perfections.
From eternity He delineated in His own mind the whole state and condition of the Church, wisely fixing her diversified fortunes in the different periods of time; dispensing the word of his grace at sundry times and in diverse manners; treating her at first more liberally…[the] families of the Patriarchs, then more strict in the nation of Israel, and at length giving her [ample] liberty in an acceptable time and a year of grace — sometimes chastising her with the rod of fatherly correction, at other times delighting her with a happy abundance of peace; now adorning her with the flowers of a grateful spring, anon afflicting her with the wasting severity of the storms of winter.
He has peculiarly exhibited his adorable wisdom in the New Testament Church which he rescued from the yoke of the ancient ceremonies and extended amongst the nations on every side; and to which after she had nobly struggled first with the pertinacity of the Jews, and then with the ferocity of the Heathen and with the wiles and artifices of Heretics, He gave the dominion of the world under Constantine the Emperor. From that period the connexion [sic] of the Beast with the Church commenced, Antichrist began gradually to prevail, and the people of God were led captive to Babylon;
[Until] by means of the blessed Reformation the Church was indulged with more auspicious times; hitherto indeed interrupted and still to be interrupted by intervals of declension, but to issue in the happy conversion of the Jews and in all the glories reserved for the Church in latter days, till, whilst religion is again declining the Judge shall appear from heaven and bring all things to their consummation.
These varied scenes which are often predicted in the prophetic books of Scripture and accurately detailed in the sacred Revelation of John, but now in a great measure fulfilled in the events themselves are presented to believers as the subject of pious meditation for the glory of God, the confirmation of faith, and the exercise of hope.
‘The righteous shall see it, and rejoice; and all iniquity shall stop her mouth. Whoso is wise, and will observe these things, even they shall understand the loving-kindness of the Lord.’ Nay, these are matters in which, ‘unto the principalities and powers in heavenly places, is made known by the Church, the manifold wisdom of God; according to the eternal purpose, which he purposed in Christ Jesus, our Lord.’
But even this is not all that is necessary. We must also cultivate fellowship with the Church of Christ by associating with her in the hearing of the word, in public prayer, in songs of praise to God, in the profession of the faith, and in the participation of the same bread and wine at the Lord’s table. We ought not merely to run but even to fly together as doves to their windows, that in us, too, those prophecies may be accomplished which describe in terms so magnificent the joyful flowing together of the nations to the Church. ‘Behold how good and how pleasant it is for brethren to dwell together in unity!'” (Herman Witsius, Sacred Dissertations)