Sa'id bin al-Musayyab and Abu Bakr bin Abd al-Rahman (may Allah have mercy on them both) said about a man who takes an oath of ila from his wife: When four months pass, it will be one divorce, but the husband has the right to take her back during the days of the waiting period.
Imam Malik (may Allah have mercy on him) said: This was also the view of Ibn Shihab al-Zuhri (may Allah have mercy on him).
This is more correct than the first narration.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الإيلاء / 15224