1 Samuel 13:12-14 – 12 I said, ‘Now the Philistines will come down against me at Gilgal, and I have not sought the favor of the Lord.’ So I forced myself, and offered the burnt offering.” 13 And Samuel said to Saul, “You have done foolishly. You have not kept the command of the Lord your God, with which he commanded you. For then the Lord would have established your kingdom over Israel forever. 14 But now your kingdom shall not continue. The Lord has sought out a man after his own heart, and the Lord has commanded him to be prince over his people, because you have not kept what the Lord commanded you.”
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Just a quick thought: Saul decided that he would offer the sacrifice because time was growing short. Besides, “God wouldn’t get all worked up about something so small as the lineage of the man who makes the sacrifice would he? Isn’t the important thing that the sacrifice is made, not how it is made?” And, as you see, Saul was wrong. Let’s be very, very careful in ever saying something like “I don’t think God is really all that concerned about whether we. . . “ God is holy. His holiness makes him concerned about every intimate detail of how we worship him.