Exodus 12:14-16, "This is a day you are to commemorate; for the generations to come you shall celebrate it as a festival to the Lord-a lasting ordinance. For seven days you are to eat bread made without yeast. On the first day remove the yeast from your houses, for whoever eats anything with yeast in it from the first day through the seventh day must be cut off from Israel. On the first day hold a sacred assembly, and another one on the seventh day. Do no work at all on these days except to prepare food for everyone to eat-that is all you may do."
Later on in verse 29 the Lord struck down all the first born in Egypt. In verse 51 all the Israelites were brought out of Egypt by their divisions.
It wasn't until a year later that the sacrificial system was instituted (Galatians 3:19). It was added because of transgressions until the Seed to whom the promise referred had come.
The fact remains that the "holy days" were part and parcel with the Levitical system
I was quoting Exodus....and now I will quote Mark. "These people honor me with their lips, but their hearts are far from me. They worship me in vain; their teachings are but rules taught by men. You have let go of the commands of God and are holding on to the traditions of men." (7:6-8)
"Speak to all the congregation of Israel, saying: 'On the tenth day of this month every man shall take for himself a lamb, according to the house of his father, a lamb for a household. And if the household is too small for the lamb, let him and his neighbor next to his house take it according to the number of the persons; according to each man's need you shall make your count for the lamb. Your lamb shall be without blemish, a male of the first year. You may take it from the sheep or from the goats. Now you shall keep it until the fourteenth day of the same month. Then the whole assembly of the congregation of Israel shall kill it at twilight. ... And thus you shall eat it: with a belt on your waist, your sandals on your feet, and your staff in your hand. So you shall eat it in haste. It is the Lord's Passover. For I will pass through the land of Egypt on that night, and will strike all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgment: I am the Lord. Now the blood shall be a sign for you on the houses where you are. And when I see the blood, I will pass over you; and the plague shall not be on you to destroy you when I strike the land of Egypt. So this day shall be to you a memorial; and you shall keep it as a feast to the Lord throughout your generations. You shall keep it as a feast by an everlasting ordinance." (Exodus 12:3-6, 11-14).
The commandment that God gave to Israel as an "everlasting ordinance" was not just unleavened bread, as your selective quote would seem to indicate without checking the context. The entire passage describes the "everlasting ordinance" of the bloody passover and unleavened bread together.
Just as Christ is our passover and has fulfilled the laws demand of blood sacrifice, so Christ is our "unleavened bread". When we feast on Him we spiritually partake of the ordinances, since they are fulfilled in Him.
It wasn't until a year later that the sacrificial system was instituted
So, according to your theory what was going on in Exodus 12:3ff with the bloody sacrifice of a lamb?
What purpose then does the law serve? It was added because of transgressions, till the Seed should come to whom the promise was made; and it was appointed through angels by the hand of a mediator.
Galatians 3:19 does not say the "sacrificial law" as you read it. It does not differentiate between the parts of the ceremonial laws; sacrifices, holy days, etc. You are sorely misinterpreting the texts.