Deuteronomy 12:8

Moses points out that heretofore they had not observed the prescribed order in their worship, because during their migratory life in the wilderness it had been impossible to do so. During their wanderings there were doubtless times when the tabernacle was not set up for days together, and when the daily sacrificeNumbers 28:3, together with many other ordinances, were necessarily omitted (compareJoshua 5:5). This consideration must be carefully borne in mind throughout Deuteronomy. It illustrates the necessity for a repetition of very much of the Sinaitic legislation, and suggests the reason why some parts are so urgently reiterated and impressed, while others are left unnoticed.