The readings for the second Sunday in Lent are taken from Genesis 12:1-9; Romans 4:1-8, 13-17; and John 3:1-17.
Genesis records how God established a particular relationship with Abraham. This relationship is parabolic. God calling Abraham out of his country and people is parallel to God regenerating us from above, as Jesus tried to explain to Nicodemus. According to our regenerate souls, we are children of God (1 John 3:1) and citizens of the kingdom of heaven. We live in our human nature as in a tent and in this world as sojourners, stewards, and ambassadors.
In his letter to the Christians in Rome, Paul brings to mind the life of Abraham as the model for our own—especially to prove that our redeemed life and future with God comes because of the gracious working of God, not our work. Faith, belief, and trust are the opposite of work. Abraham rested in the promises of God to him, promises God proved by giving Abraham and Sarah a son when such a new life was impossible for them.
John’s Gospel contrasts the restless assertion of the human ego at work in Nicodemus. He knows that Jesus is extraordinary, but comes to Jesus to argue his own thinking rather than coming to know the mind and work of God. Jesus explains that His redeeming work does for all of us what God had done miraculously in history by raising the dead and bringing about conceptions for couples who could not conceive children. We ARE the authentic children of Abraham, God IS our Father, the essence of our person IS a soul regenerated in the image of Christ, and confirmed by the means of grace (Word and sacraments).
To go with this summary, you can also watch a sermon that I preached on the text here (the sermon begins at 28:40).