Whenever Ibn Umar was asked about someone who had pronounced three divorces, he would say, "If you had divorced her once or twice, then indeed the Prophet ﷺ commanded me with this. But if you divorced her three times, she becomes unlawful to you until she marries another husband."
وقال الليث
كان ابن عمر إذا سئل عمن طلق ثلاثا قال لو طلقت مرة أو مرتين فإن النبي ﷺ أمرني بهذا، فإن طلقتها ثلاثا حرمت حتى تنكح زوجا غيرك.