“The man said to Eli, ‘I am the one who came from the battle line. Indeed, I escaped from the battle line today.’ And he said, How did things go, my son?” Then the one who brought the news replied, ‘Israel has fled before the Philistines and there has also been a great slaughter among the people, and your two sons also, Hophni and Phinehas, are dead, and the ark of God has been taken'” (1 Samuel 4:16-19, NASB).
When the Philistines captured the ark of the covenant from the Israelites, it was the direct result of the presumption of the Israelites that God was on their side no matter what they did or didn’t do.
The ark of the covenant was the visible sign of the presence and power of God. Until this time the ark had been housed in the tabernacle (tent sanctuary) at Shiloh, where it resided since the Israelites entered the promised land (Joshua 18:1). Now, Israel was disastrously defeated by the Philistines and the elders of Israel realized that the defeat was the work of the Lord.