Finding the days God set out as holy is relatively easy, as the Bible records them in several places. Here in Leviticus, God establishes himself as the creator of everything for those who had forgotten. He sets aside Saturday for a day of worship and rest, just as he did at the beginning of the world. It is to be observed every seven days, whereas the other holy days are to be kept annually, each in their own season.
Leviticus 23:1-3 King James Version
1 And the Lord spake unto Moses, saying, 2 Speak unto the children of Israel, and say unto them, Concerning the feasts of the Lord, which ye shall proclaim to be holy convocations, even these are my feasts. 3 Six days shall work be done: but the seventh day is the sabbath of rest, an holy convocation; ye shall do no work therein: it is the sabbath of the Lord in all your dwellings.
Because the Isrealites had lost much of their heritage during their captivity in Egypt, God reinstates his calendar so they can keep his days promptly. People remember better with hands-on learning and God institutes his first holy day with an activity. Foreshadowing the salvation Jesus would bring as our passover lamb, God has the Israelites kill their own lamb and sprinkle its blood on their doorposts. This passover sacrifice’s blood was poignant for them as it showed their willingness to accept God as their saviour, just as the blood of Jesus, our passover lamb, saves us from death and gives us everlasting life. Can putting the sacrifice of Jesus into its historical setting make it more relevant to us? Why did God use his old covenant holy days to foreshadow his new covenant salvation? What more can we learn from them?
Exodus 12:1-6 King James Version
1 And the Lord spake unto Moses and Aaron in the land of Egypt saying, 2 This month shall be unto you the beginning of months: it shall be the first month of the year to you. 3 Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house: 4 And if the household be too little for the lamb, let him and his neighbour next unto his house take it according to the number of the souls; every man according to his eating shall make your count for the lamb. 5 Your lamb shall be without blemish, a male of the first year: ye shall take it out from the sheep, or from the goats: 6 And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening. 7 And they shall take of the blood, and strike it on the two side posts and on the upper door post of the houses, wherein they shall eat it.