The scriptures are the only external guide in matters of religion; they are the road signs we should follow. John Gill writes:
Thus saith the Lord, Stand ye in the ways and see, and ask for the old paths, where is the good way, and walk therein; and ye shall find rest for your souls. (Jeremiah 6:16)
In this chapter the destruction of Jerusalem by the Babylonians is threatened and foretold, and the causes of it assigned; in general, the great abounding of sin and wickedness among the people; and in particular, their neglect and contempt of the word of God; the sin of covetousness, which prevailed among all sorts; the unfaithfulness of the prophets to the people, and the people’s impenitence and hardness of heart; their want of shame, their disregard to all instructions and warnings from the Lord, by the mouth of his prophets, and their obstinate refusal of them; which last is expressed in the clause following the words read; and which, though an aggravation of it, show the tender regard of the Lord to his people, and may be considered as an instruction to such who had their doubts and difficulties in religious matters; who were halting between two opinions. . . .
The direction given to stand in or on the ways, etc. to do as men do when they are come to a place where two or more ways meet, make a stand, and view the roads, and see which they should take; they look about them, and consider well what course they should steer; they look up to the way-marks, or way-posts, and read the inscriptions on them, which tell them whither such a road leads, and so judge for themselves which way they should go. Now in religious matters, the way-marks or way-posts to guide and direct men in the way are the scriptures, the oracles of God, and they only. Not education-principles. It is right in parents to do as Abraham did, to teach their children to keep the way of the Lord (Gen. 18:19). The direction of the wise man is an exceeding good one; Train up a child in the way he should go, and when he is old, he will not depart from it (Prov. 22:6); that is, easily and ordinarily: and it becomes Christians under the gospel dispensation to bring up their children in the nurture and admonition of the Lord (Eph. 6:4); and a great mercy and blessing it is to have a religious education; but then, as wrong principles may be infused as well as right ones, into persons in their tender years, it becomes them, when come to years of maturity and discretion, to examine them, whether they are according to the word of God, and so judge for themselves, whether they are to be abided by or rejected. I know it is a grievous thing with some persons to forsake the religion they have been brought up in; but upon this foot, a man that is born and brought up a Turk or a Jew, a Pagan or a Papist, must ever continue so. Sad would have been the case of the apostle Paul, if he had continued in the principles of his education; and what a shocking figure did he make whilst he abode by them. . . .
Nor are the customs of men a rule of judgment, or a direction which way men should take in matters of religion; for the customs of the people are for the most part vain (Jer. 20:3), and such as are not lawful for us, being Christians, to receive or observe (Acts 16:21); and concerning which we should say, We have no such custom, neither the churches of God (1 Cor. 11:16). Custom is a tyrant, and ought to be rebelled against, and its yoke thrown off.
Nor are the traditions of men to be regarded; the Pharisees were very tenacious of the traditions of the elders, by which they transgressed the commandments of God, and made his word of no effect; and the apostle Paul, in his unregenerated state, was zealous of the same; but neither of them are to be imitated by us: it is right to observe the exhortation which the apostle gives, when a Christian (Col. 2:8); beware lest any man spoil you through philosophy and vain deceit, after the traditions of men, after the rudiments of the world, and not after Christ.
Take care you are not imposed upon, under the notion and pretense of an apostolic tradition; unwritten traditions are not the rule, only the word of God is the rule of our faith and practice. (“The Scriptures: The Only Guide in Matters of Faith”)