The first Passover was a solemn promise that God was in process of delivering his people from slavery in Egypt.

The Passover Jesus observed right before his death was a solemn promise that God was in process of delivering his people from slavery to sin.

Exodus 12:1-13 NKJV

[1] Now the Lord spoke to Moses and Aaron in the land of Egypt, saying, [2] “This month shall be your beginning of months; it shall be the first month of the year to you. [3] Speak to all the congregation of Israel, saying: ‘On the tenth of this month every man shall take for himself a lamb, according to the house of his father, a lamb for a household. [4] 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. [5] Your lamb shall be without blemish, a male of the first year. You may take it from the sheep or from the goats. [6] 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. [7] And they shall take some of the blood and put it on the two doorposts and on the lintel of the houses where they eat it. [8] Then they shall eat the flesh on that night; roasted in fire, with unleavened bread and with bitter herbs they shall eat it. [9] Do not eat it raw, nor boiled at all with water, but roasted in fire—its head with its legs and its entrails. [10] You shall let none of it remain until morning, and what remains of it until morning you shall burn with fire. [11] 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. [12] ‘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. [13] 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.

The blood of the lambs covered the entrances of each home in the land of Goshen and the spirit of death saw this blood and did not enter those homes as it went out  

The fire represents the Holy Spirit. Roasting the Lamb focused not only on the sacrifice of the lamb to save God’s people, but on the sanctification of the Spirit of God. This was a new thing and it began the year and continues to begin the year for the Jewish people. 

Exodus 12:14-20 NKJV

[14] ‘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. [15] Seven days you shall eat unleavened bread. On the first day you shall remove leaven from your houses. For whoever eats leavened bread from the first day until the seventh day, that person shall be cut off from Israel. [16] On the first day there shall be a holy convocation, and on the seventh day there shall be a holy convocation for you. No manner of work shall be done on them; but that which everyone must eat—that only may be prepared by you. [17] So you shall observe the Feast of Unleavened Bread, for on this same day I will have brought your armies out of the land of Egypt. Therefore you shall observe this day throughout your generations as an everlasting ordinance. [18] In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty-first day of the month at evening. [19] For seven days no leaven shall be found in your houses, since whoever eats what is leavened, that same person shall be cut off from the congregation of Israel, whether he is a stranger or a native of the land. [20] You shall eat nothing leavened; in all your dwellings you shall eat unleavened bread.’ ”

Leven represents sin. They were to remove sin from their homes (and physically any yeast or items made with yeast as a physical representation of their dedication to remove  sin) 

Exodus 12:21-28 NKJV

[21] Then Moses called for all the elders of Israel and said to them, “Pick out and take lambs for yourselves according to your families, and kill the Passover lamb. [22] And you shall take a bunch of hyssop, dip it in the blood that is in the basin, and strike the lintel and the two doorposts with the blood that is in the basin. And none of you shall go out of the door of his house until morning. [23] For the Lord will pass through to strike the Egyptians; and when He sees the blood on the lintel and on the two doorposts, the Lord will pass over the door and not allow the destroyer to come into your houses to strike you. [24] And you shall observe this thing as an ordinance for you and your sons forever. [25] It will come to pass when you come to the land which the Lord will give you, just as He promised, that you shall keep this service. 

So every year, at the begining of the Hebrew year, Israel continued to observe Passover with the sacrifice of the Passover lamb. 

Jesus observed Passover with his disciples shortly before his death. He related Passover directly to himself, telling the disciples what we know of as the tradition of observing communion. 

Matthew 26:26-30 NKJV

[26] And as they were eating, Jesus took bread, blessed and broke it, and gave it to the disciples and said, “Take, eat; this is My body.” [27] Then He took the cup, and gave thanks, and gave it to them, saying, “Drink from it, all of you. [28] For this is My blood of the new covenant, which is shed for many for the remission of sins. [29] But I say to you, I will not drink of this fruit of the vine from now on until that day when I drink it new with you in My Father’s kingdom.” [30] And when they had sung a hymn, they went out to the Mount of Olives. 

You see Jesus’ body was about to be broken and his blood spilled for our sins. The unleavened bread represented Jesus, a man without sin and God in the flesh, being broken for us. The wine represents the blood of Jesus spilled for our sins. Jesus HIMSELF was the Passover lamb, roasted in the fire of the Holy Spirit and prepared as a sacred offering once and for all for the forgiveness of our sins.  

The temple was destroyed in AD 70, Several years after the death and resurrection of Christ. The Jewish people now do not eat lamb at Passover since the lamb cannot be sacrificed in the temple. They eat a roasted egg instead (representation of Ishtar?) and have a roasted lamb bone on the plate to mourn the lack of temple sacrifices. 

Knowing that the Lamb of God who takes away the sins of the world has been sacrificed once and for all for the remission of sins, I would be observing Passover in celebration now or Jesus and what he has done. The temple sacrifice is no longer necessary for our forgiveness and protection. Jesus has done the work and completed it. 

Hebrews 10:10-18 NKJV

[10] By that will we have been sanctified through the offering of the body of Jesus Christ once for all.  [11] And every priest stands ministering daily and offering repeatedly the same sacrifices, which can never take away sins. [12] But this Man, after He had offered one sacrifice for sins forever, sat down at the right hand of God, [13] from that time waiting till His enemies are made His footstool. [14] For by one offering He has perfected forever those who are being sanctified. [15] But the Holy Spirit also witnesses to us; for after He had said before, [16] “This is the covenant that I will make with them after those days, says the Lord: I will put My laws into their hearts, and in their minds I will write them,” [17] then He adds, “Their sins and their lawless deeds I will remember no more.” [18] Now where there is remission of these, there is no longer an offering for sin. 

Hebrews 10:19-25 NKJV

[19] Therefore, brethren, having boldness to enter the Holiest by the blood of Jesus, [20] by a new and living way which He consecrated for us, through the veil, that is, His flesh, [21] and having a High Priest over the house of God, [22] let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience and our bodies washed with pure water. [23] Let us hold fast the confession of our hope without wavering, for He who promised is faithful. [24] And let us consider one another in order to stir up love and good works, [25] not forsaking the assembling of ourselves together, as is the manner of some, but exhorting one another, and so much the more as you see the Day approaching.