The tribe of Ephraim (chapter 12) was the leading tribe of northern and central Israel. There was an element of pride in this position and she believed that everything that happened in Israel needed her participation and approval.
We saw this before in the conflict between Gideon and the Midianites (chapter 8). In that situation, Gideon mollified Ephraim’s hurt pride with superior diplomacy. Jephthah, however, was not so inclined to be diplomatic – especially with people who were threatening to “burn his house down.” “House” in the Old Testament doesn’t just mean dwelling, but can also refer to one’s family – particularly if he is a ruler. If this latter idea is what Ephraim meant, the threat was against Jephthah’s entire family line and his judgeship.
Jephthah is a strong and wise leader. He first explains the situation, tells them that he did call on them for help but they did not reply. When they ignore the facts and maintain their belligerence, Jephthah cuts them off at the knees. Ephraim is so decimated that she never again regains her former prominence.
Pride is at the heart of this fall. They should have seen the work of God in the story of Jephthah and rejoiced, but blinded by their own self-importance, they discount the work of God because they had no part in the victory.
Whenever others do well, we will do well to congratulate them. When we diminish the success of others because we had not part in it, we fall into the trap of the Ephraimites and risk more than our pride, but also future success and opportunity.