Genesis 21:34

And Abraham sojourned in the Philistines' land many days. As he had done in other places, Genesis 12:8; Genesis 13:18, so Abraham did here. Having planted a tamarisk, a tree which grew to a remarkable height and furnished a wide shade, he proclaimed there the name of the eternal God, chiefly to his own household, but also to others that might come along this way. This he continued as long as he lived this nomadic life in the territory of the Philistines, for they considered this section a part of the country under their control. That is the chief work of the believers on earth, to praise the name, the mercy, the faithfulness of God and to proclaim His Word. Thus they do what they can to bring all men to the knowledge of the truth.