Abu Ishaq narrates from Abu Burdah (may Allah have mercy on him) that a man would say to his wife: "I have divorced you", and at times he would say: "I have taken you back." When the Prophet (peace and blessings be upon him) came to know of this, he said: "What is the matter with men that they play with the limits set by Allah?"
This is mursal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14897