What does Genesis 26:15 mean?
The previous verse told us the Philistines were envious of Isaac's enormous and growing wealth. Despite a famine which would have left most people struggling (Genesis 26:1), Isaac has managed a hundredfold return on his crops (Genesis 26:12–13). This explosive growth made Isaac and his family a dominant force in their region. This has already generated envy among the Philistines, and will soon result in fear (Genesis 26:16).As happened with Abraham (Genesis 21:25–26), water rights have now become a point of contention between Isaac and Abimelech's people. The famine in the land might have been tied to a drought; this would make arguments over wells even more heated.
Isaac, apparently, had been using wells dug by Abraham's servants in the days that Abraham lived in Gerar (Genesis 21:30). Now the Philistines had filled those wells up with dirt, to slow down Isaac's progress and keep him from using the water. When something similar happened to Abraham, the prior king had claimed ignorance and, eventually, had made a treaty with Abraham (Genesis 21:31–33). This time, Abimelech's response to the dispute over water will be much different.