سُنَنُ ابْنِ مَاجَهْ
Sunan Ibn Majah 2098
The Chapters on Expiation
One who takes an oath to follow a religion other than Islam
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ خَالِدٍ الْحَذَّاءِ، عَنْ أَبِي قِلاَبَةَ، عَنْ ثَابِتِ بْنِ الضَّحَّاكِ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ مَنْ حَلَفَ بِمِلَّةٍ سِوَى الإِسْلاَمِ كَاذِبًا مُتَعَمِّدًا فَهُوَ كَمَا قَالَ .
It was narrated that Thabit bin Ad-Dahhak said: The Messenger of Allah (ﷺ) said: 'Whoever takes an oath to follow a religion other than Islam, telling a deliberate lie, he will be as he said.'"
Sunan Ibn Majah, 2098Sahih (Darussalam)