Judges 11:29-39 / Matthew 22:1-14
Making promises are always a risky undertaking.
Because promises are made to be kept and not to be broken.
To break a promise would say much about the person's character and what the person thinks about making promises to people.
But what if one were to make a promise to God, and it is a promise that would involve a blood sacrifice?
In the 1st reading, when Jephthah made a vow to the Lord to offer the first person to meet him from the door of his house when he returned in triumph, would he be expecting that person to be his daughter, his only child?
Certainly he regretted making the promise but he had to keep the promise - "I have given a promise to the Lord, and I cannot unsay what I have said."
But in the first place, the question is that was it necessary for Jephthah to make that promise to the Lord?
The Lord did not ask him for anything. It was Jephthah himself who wanted to secure triumph over the Ammonites that made him make that promise to the Lord.
But it was the Lord who called Jephthah for the mission. So the Lord did not ask anything of him.
As Romans 8:30 would say this - "And those he predestined, he also called; those he called, he also justified; those he justified, he also glorified."
So there is nothing that we can offer to the Lord to justify ourselves. If God calls us, we only have to offer ourselves to Him as a living sacrifice. That will be enough.