See that you do everything I command you; do not add to it or subtract from it.
32. What thing soever I command. In this brief clause he teaches that no other service of God is lawful, except that of which He has testified His approval in His word, and that obedience is as it were the mother of piety; as if he had said that all modes of devotion are absurd and infected with superstition, which are not directed by this rule.
There is not any one particular precept (as I remember) in all the law of Moses so largely pressed and inculcated as this, by which they are all tied to bring their sacrifices to that one altar which was set up in the court of the tabernacle, and there to perform all the rituals of their religion; for, as to moral services, then, no doubt...
Commenting on Deuteronomy 12:5-32
What thing soever I command you, observe to do it,.... In the manner it is commanded and directed to; the laws of God, both as to matter and manner, were to be obeyed just as they were delivered: thou shall not add thereto, nor diminish from it; neither add any customs and rites of the Heathens to them, nor neglect anything enjoined on them, see Pro 30:6.