1-18:19- "For I have chosen him"
God chose Abraham to make His purposes and plan go forth. Remember, Abraham was an idolater in Ur when God chose and called him. Abraham did not worship Yahweh alone and was a broken sinful man before God called him out and made a covenant with him. God made the covenant and gave Abraham the right standing before Him. That is grace is the clearest sense, God did not have to do any of that and could have let Abraham rot in his own sin and be damned for it.
2-Getting Lot out of Sodom
Lot was a broken man who could not lead his family well. Lot was not like his uncle and a true man of faith in Yahweh. Lot was backsliding away from God when he moved his family into Sodom and even in the middle of chapter 19 tries to send his daughters into harms way. But God, in spite of all this saves him and his family from the destruction of Sodom. Again a clear act of grace shown and even told to us by God in His conversation with Abraham right before it.
3-God in His Holy Righteous judgment destroys Sodom
You might say how is this an act of grace. But think about it for a minute. God is Holy all the time and should do this to every human being who ever existed, except one, Jesus Christ. This Holy wrath of God though was poured out on the one human being who did not deserve it. That same fire and brimstone was poured out on Jesus on the cross and in grace from God, Jesus took it for US. Sodom's destruction is a clear picture of what God did to Jesus on the cross for us and WE are no better than anyone in the town of Sodom which was destroyed. Clear as day grace there.
4-Same mistake twice
How many times do we seem to commit the same sin over and over again. Abraham does when he tells Sarah to lie again and not say she is his wife. Yes they were related by blood, but more important Sarah was his wife. That is called stretching the truth which is lying. Yet God still uses this broke sinner for His purposes and keeps the covenant. Abraham breaks the covenant clear as day in chapter 20 and the covenant was only a few chapters ago in 17. Yet God in His grace keeps the covenant with Abraham and keeps His promises. Again grace in the purest sense.
I pray and hope that in the reading today you can see the grace of God. This same grace is given to us today, tomorrow, next year, and for eternity. Lets rejoice in a gracious loving God who keeps His covenant with us, in spite of our broken sinful nature and committed acts of unbelief every day.