Hadith 511510
Chapter 28: Marriage - كتاب النكاح
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّهُ قَالَ ثَلاَثٌ لَيْسَ فِيهِنَّ لَعِبٌ النِّكَاحُ وَالطَّلاَقُ وَالْعِتْقُ .
Yahya related to me from Malik from Yahya ibn Said that Said ibn al-Musayyab said, "There are three things in which there is no jest:
marriage, divorce, and setting free."
Reference Muwatta Malik 511510
USC-MSA web (English) reference : Book 28, Hadith 56