Did Jephthah sacrifice his daughter? In Judges 11, Jephthah vows to give whatever comes out of the door of his house as a burnt offering.


  Judges 11:30-40 (ESV) [emphases mine]  
  
  30 And Jephthah made a vow to the LORD and said, "If you will give the Ammonites into my hand, 31 then whatever comes out from the doors of my house to meet me when I return in peace from the Ammonites shall be the LORD’s, and I will offer it up for a burnt offering." 
  
  34 Then Jephthah came to his home at Mizpah. And behold, his daughter came out to meet him with tambourines and with dances. 
  
  39 And at the end of two months, she returned to her father, who did with her according to his vow that he had made. 



Did Jephthah really sacrifice his daughter? This clearly couldn't be
the will of God (e.g. Jeremiah 7:31, 19:5, 32:35).
What did Jephthah mean by his vow?
Surely he knew who lived in his house, and had some expectations on what could come out of the door?
This is an odd passage, since, as you noted, he would certainly have known his household.  Also, the Law of Moses strictly forbade human sacrifice, particularly the sacrifice of one's own children, categorizing it as an abomination before the Lord, so such an offering would never have been acceptable to God anyway.

It's interesting to note that the mourning of Jephthah's daughter and her companions was not for her life, but for her virginity; she would never have the blessing (it was still unequivocally considered a blessing back then) of having children.  And verse 39 says "she had never known a man" in the ESV, but the KJV renders it in present tense: "[Jephthah] did with her according to his vow which he had vowed: and she knew no man"

Taken together, these points suggest that she may have been "offered to the Lord" in a different way: as a consecrated servant of God of some sort which would preclude her getting married and having children.