Hadith 4:621
Waki’ narrated to us, from Abu Hanifa, from Hammad, from Ibrahim, regarding the fasting person who performs ablution and water enters his throat from his ablution: He said: "If he was mindful of his fast, then he must make up the day (qada). But if he was forgetful, then there is nothing upon him."
حدثنا وكيع عن أبي حنيفة عن حماد عن إبراهيم في الصائم يتوضأ فيدخل الماء حلقه من وضوئه قال إن كان ذاكرا لصومه فعليه القضاء وإن كان ناسيا فلا شيء عليه