The first four dispensations are all found in Genesis. In the first three, God held the entire human race accountable for its stewardship. The fourth brought dramatic change. God chose Abraham and Sarah to begin the family line which would one day include His Son. The change included a unique practice known as circumcision. Abraham's male family members and his male servants were required to submit themselves in order to be accounted faithful. The rest of the human race became identified as Gentiles, and they remained responsible to their governments. The nations no longer had equal standing with God, but were now expected to recognize Abraham's People as God's chosen.
God told Abraham to go from his home in Ur of the Chaldees, to a land God determined to be for His chosen people. Abraham saw two major problems with His plan. For one, the land was already occupied, and another, there was a famine at the time of his arrival. Abraham knew nothing of a God Who could create manna, multiply loaves and fishes, provide water from a rock, or turn water into wine. So he decided to pass on through the land God had chosen for him, and go to Egypt, where there was no famine. This seemed to become a pattern for Abraham and his descendants, because they repeated the demonstration of a lack of faith in God (Genesis 12:10; 26:2-3; 39:1; 48:27; and 50:15). It would eventually cost them dearly. The one exception to a family member going to Egypt that turned out to be a good thing was when Joseph took Jesus and Mary there to escape Herod's diabolical plan (Matthew 2:13-15). Not much else changed. They were still permitted to eat their choice from all animal and plant life. The only significant difference was that, for the first time, there were two distinct types of people: Jews and Gentiles.
It took only four generations before God had His fill of Abraham's family placing their trust in the bounty of Egypt, rather than trusting Him for their needs. His great, great grandson became an Egyptian slave. He lived there the rest of his life. God used another perfectly timed famine to say that He had had enough. If they loved Egypt so much, He would see to it that they got their fill of it. Following the death of Joseph, the Egyptians overpowered the Hebrew people and made them slaves for the next four hundred years.
The Dispensation of the Promised Land might be described as:
Stewardship: Abraham and Sarah's family to possess the land (Genesis 12:7; 17:19)
Foods: There was no change.
Command: Abraham's family was to dwell in the land God gave them (Genesis 12:1-3)
Response: They repeatedly trusted in Egypt (see verses in the second paragraph above)
Judgment: The Bondage They became Egyptian slaves (Genesis 15:13; Exodus 1:8-14)