The Geshurites, and the Gezrites were remnants of those seven Canaanite nations which Joshua had been commanded to destroy and take possession of their lands (Joshua 10:33; 13:2), and the Amaletikes were descends of Esau who opposed Israel’s entry into the land (Exodus 17:8). They were branches of those groups that dwelt in the wilderness, neighbouring the Ziklag region.
That is a warning to us. If I backslide – let's say it takes the form of spiritual coldness, and I don't do anything about that spiritual coldness, and I let it go on day after day. I leave off prayer, or at any rate earnest prayer, and witness and service; I do everything limply. I become spiritually cold, and my love for Christ grows so small. Well, I shall fill my interests and apply my energies to other things. Home and family will take up a much larger share of my concerns. Perhaps career, pleasures, television; it could be any number of things. I am now in a spiritually cold state and condition, and I am giving more attention to the material things and the worldly things. Yes, but I fool myself. I don't actually give up my Sunday School class. I don't actually give up attendance at Sunday services. There are certain things I keep, because I am convincing myself that I am not spiritually cold; there is nothing the matter with me, and I don't want to appear that way to other believers. So I will speak to them as though nothing in the world is the matter, and I have the same zeal and earnestness as ever. David does something like this when he goes into the land of the Philistines to get security there. He has ceased to have faith in God's promise to protect him and keep him, even in the place of danger, and yet while he is with the Philistines, he will convince himself that he is in the service of the Lord, and he is carrying his commission. He has been anointed as the defender of Israel, and he will go and mount raiding parties against Israel's enemies down there in the south. A strange compromise. We try to quieten our own unrest and our own consciences.
As soon as a Christian compromises, he finds he has got to compromise more and more. Even famous evangelists, whose names have been well-known; once they started to compromise, it led them into more and more until they were virtually carried away from the faith and discredited the work of God altogether. At this point David is almost in this position, but he will be delivered by God.