Psalm 105 Part 3 

Vs12-15 refers to the patriarch’s seasons of wandering and God’s protection over them. Abraham came from Ur of the Chaldeans and journeyed to Egypt (Gen11-12.) Jacob also lived for many years with Laban in the land of the people of the East. God ‘permitted no one to do them wrong:’ because they were sacred persons. In all their wanderings among the nations, God protected them. He even rebuked kings for their sakes.  

The great famine that came upon the greater region in the days of Joseph (vs16-22) was no accident. God ‘called’ the famine. Testing is the deepest meaning of affliction & God expects us to trust Him when His promises seem contradicted by circumstances. This is a true faith that is a saving faith. David understood that the injustice and misfortune which came upon Joseph was ordained by God so that in His plan he could be ‘sent ahead’ to Egypt to save the patriarchs (and the whole region) from famine. Joseph’s iron fetters were preparing him to wear chains of gold, and making his feet ready to stand in high places. It is so with all the Lord’s afflicted, they too shall one day step from their afflictions to their thrones.  
After God sent Joseph ahead, He took the people of Israel into the land of Egypt for their own provision and protection as a people, v23-25.  
In order to understand the deliverance plagues outlined in vs23-36 we need to understand that they were directed against the gods and goddesses of Egypt and were intended to show the superiority of the God of Israel to the Egyptian gods. 

Darkness vs Ra, the sun God & Nut the sky goddess.  Bloody waters vs Osiris & Khnum, gods of the Nile. Frogs vs Hekt, the frog goddess of fertility. Swarms of flies and lice vs Uatchit the fly-god. Hail vs Geb, god of the earth and Nepri, goddess of grain & Anuibis, guardian of the fields. Locusts vs Shu, god of the atmosphere & Min, deity of the harvest. Eight of the 10 plagues are listed, but not in the correct order. Pharoah is not mentioned.