In the Bible times, what was a feast?
A feast was a meal of some kind which brought great joy to the participants. It was often used to remember some past event or to look forward in hope to some future event.
What was the first feast which God called the Israelites to celebrate?
The first feast was the Passover.
What was the Passover feast?
The Passover was a meal in which the Jewish people participated to celebrate their deliverance from Egypt as is clear in these verses:
And when your children say to you, "What does this rite mean to you?" you shall say, "It is a Passover sacrifice to the LORD who passed over the houses of the sons of Israel in Egypt when He smote the Egyptians, but spared our homes." (Exodus 12:26-27)
When was the Passover celebrated?
The Passover was celebrated in the first month. On the tenth day of this month, each Israelite family chose a lamb.
Speak to all the congregation of Israel, saying, 'On the tenth of this month they are each one to take a lamb for themselves, according to their fathers' households, a lamb for each household. (Exodus 12:3)
This lamb had to be:
flawless and without any blemish;
either a sheep or a goat;
one year old.
Now if the household is too small for a lamb, then he and his neighbor nearest to his house are to take one according to the number of persons in them; according to what each man should eat, you are to divide the lamb. 'Your lamb shall be an unblemished male a year old; you may take it from the sheep or from the goats. (Exodus 12:4-5)
This lamb was kept with the family until the fourteenth day of the month on which day it was killed.
You shall keep it until the fourteenth day of the same month, then the whole assembly of the congregation of Israel is to kill it at twilight. (Exodus 12:6)
Some of the blood from this lamb was smeared on the sides and top of the door frames of the house.
Moreover, they shall take some of the blood and put it on the two doorposts and on the lintel of the houses in which they eat it. (Exodus 12:7)
That same night, the lamb was roasted and eaten with unleavened bread and bitter herbs. The key factor here was haste. The lamb was not to be savored and lingered over. All the family was to be fully dressed, with their sandals on, and their walking stick in their hand. They were to eat "on the run" as we say. Any leftovers were burned.
They shall eat the flesh that same night, roasted with fire, and they shall eat it with unleavened bread and bitter herbs. 'Do not eat any of it raw or boiled at all with water, but rather roasted with fire, both its head and its legs along with its entrails. 'And you shall not leave any of it over until morning, but whatever is left of it until morning, you shall burn with fire. 'Now you shall eat it in this manner: with your loins girded, your sandals on your feet, and your staff in your hand; and you shall eat it in haste--it is the LORD'S Passover. (Exodus 12:8-11)
What is the higher meaning of this lamb, the unleavened bread, the herbs, etc.?
The Bible does not explicitly identify these meanings, but neither is it difficult to discover. Edersheim quotes Gamaliel saying,
Whoever does not explain three things in the Passover has not fulfilled the duty incumbent on him. These three things are: the Passover lamb, the unleavened bread, and the bitter herbs. The Passover lamb means that God passed over the blood-sprinkled place on the houses of our fathers in Egypt; the unleavened bread means that our fathers were delivered out of Egypt (in haste); and the bitter herbs mean that the Egyptians made bitter the lives of our fathers in Egypt. source
What are the four cups of the Passover celebration?
This was not something originally commanded by God when He first instituted the Passover. The Jews added this detail later suggesting that these each of these cups corresponded to the promises given in Exodus 6:6-7:
I will bring you out from under the burdens of the Egyptians,
I will deliver you from their bondage,
I will also redeem you with an outstretched arm and with great judgments,
I will be your God; and you shall know that I am the LORD your God, who brought you out from under the burdens of the Egyptians.
Jesus celebrated the Passover with these four cups. source
When was the feast of weeks?
This was