Then the Lord hears their groaning and remembers His covenant with Abraham, Isaac and Jacob, to give them the land of Canaan.
The Lord calls Moses and appoints him as the one who will bring the Israelites out of Egypt. However, the pharaoh refuses to let them go.
Because of this refusal God strikes Egypt with ten plagues. The tenth plague is the killing of every firstborn in the land of Egypt.
The Israelites will not be touched by this plague if they put some of the blood of a slaughtered lamb on the sides and tops of the doorframes of their houses. When the Lord sees the blood, He will pass over then and spare their firstborn.
Pascha or Pesach means:"to pass over".
On the painting the firstborn son is looking at his father who applies the blood on the doorposts. His life is at stake.
Pascha or Passover is the foreshadowing of the sacrifice of Christ Jesus, the Lamb of God, Who gave His blood for sinners, and died to reconcile to God those who believe in Him and hide behind His blood.
1 Corinthians 5 verse 7.
After the death of Joseph and his brothers their descendants become numerous in Egypt. As time goes by a new pharaoh, who never knew Joseph, comes to power. He oppresses the Israelites with forced labour.