BT Bek 47a(55) :כיון דאי בעי לה הויא לה זרה‏ : as soon as she had sexual intercourse (with a pagan: understand איבעילה) she became a 'stranger' [i.e. disqualified from consecrated objects; v. Lev 22:12]
See the entire entry for bˁl vb. to have sexual intercourse