Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The ila' (an oath to stay away from one's wife) of the people of the Jahiliyyah used to be for one or two years. Then Allah Almighty fixed a term for ila', so whoever's ila' is for less than four months, it does not count as ila'.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11308