Muwatta Malik 677

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ كَانَ يَقُولُ مَنِ اسْتَقَاءَ وَهُوَ صَائِمٌ فَعَلَيْهِ الْقَضَاءُ وَمَنْ ذَرَعَهُ الْقَىْءُ فَلَيْسَ عَلَيْهِ الْقَضَاءُ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, "If some one makes himself vomit while he is fasting he has to make up a day, but if he cannot help vomiting he does not have to make up anything

Reference

Muwatta Malik 677

In-book

Book 18, Hadith 48