(224) Chapter: Matters relating to As-Saum (Fasting)

Laqit bin Sabirah (May Allah be pleased with him) reported:
I requested the Messenger of Allah (PBUH) to talk to me about ablution. He said, "Perform the Wudu' well (by washing those parts of the body, such as the face, hands and feet beyond what is required, like washing the hands up to the upper-arm instead of the elbow). Cleanse the base of your fingers and sniff water deep into the nose except when you are observing fast.''
[Abu Dawud and At-Tirmidhi].

Commentary: Ordinarily, it is necessary for Wudu' that one should pass water through the nose and rinse mouth thoroughly. But when one is observing Saum, he has to take care that water does not go down the throat through the nose as this nullifies the Saum.