Midrash su Esodo 29:31

2) "upon whose head the oil of anointment has been poured": What is the intent of this? Because it is written (Shemoth 29:31) "Seven days shall he anoint his sons, who ministers in his stead put them on, when he comes to the tent of meeting to minister in the holy place," I might think (that he is ordained as high-priest) only if he is anointed for seven days and invested (in the garments) for seven days. Whence do I derive that the same applies if he is anointed for seven and invested for one, or anointed for one and invested for seven, or if he is anointed for one and invested for one — even for one moment? From "upon whose head the oil of anointment has been poured" — even for one moment; "and who has been invested to wear the garments" — even for one moment.

Similarly, though Scripture states: And the priests shall kindle wood upon it every morning (Lev. 6:5), it is written: And Lebanon is not sufficient fuel (Isa. 40:16). This was stated so that one might receive a reward for doing so. Similarly, it says: The one lamb thou shalt offer in the morning (Num. 28:4), though it has already been said: Nor the beasts thereof sufficient for burnt-offerings (Isa. 40:16). This indicates that you may receive a reward (for its observance). Let them make Me a Sanctuary that I may dwell among them (Exod. 25:8) may be explained in a like manner. Has it not been written already Do not I fill heaven and earth (Jer. 23:24)? This commandment was imposed upon you so that you would receive a reward (for building a Sanctuary). And Moses said unto the people: Remember this day (Exod. 13:3). Scripture states elsewhere: That thou mayest remember the day when thou camest forth out of the land of Egypt all the days of thy life (Deut. 16:3). Does this mean that they were to remember it only during the day and not at night? Ben Zoma interpreted the verse That thou mayest remember the day when thou came forth … all the days of your life to mean that the days of your life refers to the daytime, while all the days of your life alludes to night time.