Suhayl bin Abi Salih narrates from his father: I asked 12 noble Companions (may Allah be pleased with them) about a man who makes ila', and they said: There is nothing upon him, but when four months have passed, the one who made the ila' will be made to stand; if he returns (to his wife), that is fine; otherwise he must divorce.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الإيلاء / 15209