Al-Qasim bin Muhammad (may Allah have mercy on him) said that a man declared a woman to be like his mother if he married her; Sayyiduna Umar (may Allah be pleased with him) said that he should marry that woman but not go near her before paying the expiation for zihar.
This is munqati' (broken); al-Qasim bin Muhammad did not meet Umar bin al-Khattab (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الظهار / 15252