Shavuot is the actual biblical feast the Apostles celebrated at Pentecost when the Holy Spirit was poured out. It marked the giving of the Mosaic Law on Mount Sinai. And it foreshadows that day when God inscribes His Law on our hearts - through His Holy Spirit.
In the night that God delivered Israel out of Egypt, God provided an unusual and unprecedented means of protection from certain death: the blood of a 1 year old lamb had to be applied around the door frame. This lamb that the Israelites slaughtered and ate was an Image of the true Lamb of God that was to come. Read more on the significance of Passover and how Jesus became our very own Passover.