After Abraham agreed to the treaty between him and Abimelech, the Bible records that Abraham planted a grove (tamarisk trees) at Beersheba, and there he worshiped (called on) the Lord, the everlasting God. (Genesis 21:33). A treaty with an earthly king had been agreed upon, but Abraham knew that there was to be more that needed to be done. And what was that? He planted a grove (of Tamarisk trees) and called on the name of the Lord, the everlasting God. Planting a tree is something that is permanent with roots that secure the tree to the ground. In other words, Abraham worshipped God at the end of the treaty he made with man (the king of Gerar).

Points to ponder:
When agreements with men are ratified, take a moment to thank God and worship him, calling out his name. We should be like fruitful trees planted by rivers of water (Psalm 1:3), yielding the fruit of the spirit in and through our lives (Galatians 5:22-23), rooted in Christ abounding in thanksgiving (Colossians 2:7), worshipping God.  The real treaty is the treaty of worshipping the Lord and that of what we make with man.

Genesis 21:33-34 (KJV)
33 And Abraham planted a grove in Beersheba, and called there on the name of the Lord, the everlasting God.
34 And Abraham sojourned in the Philistines’ land many days.

Colossians 2:7 (KJV)
Rooted and built up in him, and stablished in the faith, as ye have been taught, abounding therein with thanksgiving.