Asim bin Laqit bin Sabirah narrates from his father: I submitted, "O Messenger of Allah! (peace be upon him), please tell me about ablution (wudu)." So the Prophet (peace be upon him) said: "Perform ablution well. Clean between the fingers and put water into the nose thoroughly, unless you are fasting (then the ruling is different)."
Hadith Referenceصحیح ابن حبان / كتاب الطهارة / 1087
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صحيح أبي داود» (130).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده جيد