بُلُوغُ الْمَرَامِ
Bulugh al-Maram 1077
Marriage
وَلِلْحَارِثِ اِبْنِ أَبِي أُسَامَةَ : مِنْ حَدِيثِ عُبَادَةَ بْنِ اَلصَّامِتِ رَفَعَهُ : { لَا يَجُوزُ اَللَّعِبُ فِي ثَلَاثٍ : اَلطَّلَاقُ , وَالنِّكَاحُ , وَالْعِتَاقُ , فَمَنْ قَالَهُنَّ فَقَدَ وَجَبْنَ } وَسَنَدُهُ ضَعِيفٌ [1] .
al-Harith bin Abu Usamah reported from the Hadith of 'Ubadah bin as-Samit [RA) - tracing it to the Prophet (ﷺ): "It is not permissible to play in three things: divorce, marriage and emancipation. Therefore, whoever pronounce (either of) them, they certainly become binding." [Its chain of narrators is Da'if (weak)].
Sunnah.com reference: Book 8, Hadith 132