Two timetables were about to fit together.  About 1,500 years earlier, the blood of a sacrificed lamb was smeared around the doors of God's people in Egypt (Exodus 12:21-23).  The threat of death was coming to every house in the country, but God said, "... when I see the blood I will pass over you" (Exodus 12:13).  God commanded that a lamb could substitute for the life of the firstborn in every believing household; and then they would all be set free from slavery in Egypt.

They also baked unleavened bread, bread without yeast which would last for several days as they crossed the Red Sea and started the wilderness pilgrimage.  So, the annual commemoration of that event was called 'The Passover', which commenced the 'Feast of Unleavened Bread'.  And every year a lamb had to be slaughtered as a reminder of God's salvation.
 
That year, Jesus was not only going to celebrate Passover, but He would also be the Lamb of God ready to be sacrificed.  Only hours after the events in this chapter, Jesus would be dead: the substitute taking away the sins of the world (John 1:29).  In God's plan, it had to happen. Jesus must be sacrificed.  There was no other way.  As Jesus said, "The Son of Man must suffer many things and be rejected by the elders, chief priests and teachers of the law, and he must be killed and on the third day be raised to life." (Luke 9:22).
 
Many people miss the main purpose of Jesus' life.  They may think He was a good man, a teacher, a miracle worker, an example to follow, a wise speaker and the personification of love.  Yes, He was all that, but not just that.  His principal appointment as the Christ was to be God's sacrificial Lamb.  The sins of all the people of all the world for all time were laid on Him, and He accepted responsibility for them (1 John 2:2), so that those who believe in Him shall not perish in God's judgement against sin but have everlasting life (John 3:16).  Religion which tries to follow Jesus, without believing in Him as the sacrificed Lamb of God, is eternally futile.  That is why we need to help those whose mind is fogged; they need to hear the gospel, for: "Salvation is found in no-one else, for there is no other name under heaven given to mankind by which we must be saved." (Acts 4:12).  Note the imperative, "must", yet again.  This is a royal command.  So, we must tell the Good News so that others will know how to be saved. www.crosscheck.org.uk may be a great help to you in explaining it, and to your friends in understanding and responding.