I found the following comments on Leviticus 6-7 helpful:
Jesus said that God must be worshipped in spirit and in truth. And it has become commonplace to contrast spirit and form as if they were incompatible in worship. “The letter killeth but the Spirit giveth life” is a text that out of context (2 Cor 3:6) can be used to justify slapdash leading of services and other Christian activities. Spontaneity and lack of preparation is equated with spirituality. Lev. 6-7 denies this: care and attention to detail are indispensable to the conduct of divine worship. God is more important, more distinguished, worthy of more respect than any man; therefore we should follow his injunctions to the letter, if we respect him.
A glance at the performing arts dispels the illusion that a great and spirited performance can be achieved without practice and attention to detail. Indeed great actors and musicians spend hours studying and rehearsing the works they are to perform, so that they can recapture the spirit of the author and convey it in their performance. Audiences expect performers to aim at perfection in the concert hall. Worship is also a performance, a performance in honor of almighty God. As no orchestra can give of its best without a competent conductor and meticulous rehearsal, so no congregation is likely to worship our holy God in a worthy manner without careful direction by a well-instructed minister.
Gordon J. Wenham, Commentary on Leviticus.