Thabit bin Ubayd, who was a freed slave of Zayd bin Thabit (may Allah be pleased with him), says that 12 noble Companions (may Allah be pleased with them) say that ila' is not a divorce until the one who made the ila' is made to stand before the judge.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الإيلاء / 15208