Ikrimah narrates from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that zihar and divorce do not occur before marriage.
(b) In the Book of Divorce it is narrated from the Prophet (peace and blessings be upon him), Sayyiduna Ali (may Allah be pleased with him) and Sayyiduna Ibn Abbas (may Allah be pleased with them both): "There is no divorce before marriage, and zihar has the same meaning."
The opposite of this has been narrated from Umar bin al-Khattab (may Allah be pleased with him) with a mursal chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الظهار / 15251