It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): "If a man makes an oath of abstinence (ila) from his wife and does not approach her before four months, then one irrevocable divorce (talaq bain) will take place. Then the woman will observe the waiting period ('iddah) for three menstrual cycles. And during the 'iddah, if they wish, they can remarry."