What breaks wudu, and what does not

You do not have to redo wudu before every prayer. If your wudu is still intact, pray. If something has broken it, redo it. Here is what breaks it, agreed upon by the majority of scholars.

What definitely breaks wudu

• Urine or stool passing from the front or back. This is obvious.
• Passing gas. Yes, even if silent. Yes, even if you are already in the middle of wudu. Redo it.
• Deep sleep, especially lying down. A short doze while upright is debated.
• Losing consciousness, whether from fainting, general anaesthetic, or otherwise.
• Touching your own private parts directly with no barrier (the Shafi'i and Hanbali schools say this breaks wudu; the Hanafi school says it does not).
• Anything unusual coming out of the body in large amounts, such as blood (this is debated; Hanafis say yes, Shafi'is say no).
• For women, menstrual and postnatal bleeding. These also require ghusl before resuming prayer.

What does NOT break wudu

• Eating. Including meat (there is a specific old ruling about camel meat that does break it, but eating other foods does not).
• Drinking water or anything halal.
• Touching a woman or being touched by one (the majority position; the Shafi'i school takes it more strictly).
• Saying anything, including names or words.
• Small drops of blood from a cut or nosebleed (most schools).
• Normal social contact, handshakes, hugs with close family.

When you are uncertain

There is a famous ruling that if you are in wudu and you doubt whether it has broken, you stay in wudu. Certainty is not lifted by doubt. Only redo it if you actually know.

A lot of new Muslims fall into waswasa (whispers from Shaytan) about wudu, obsessing over whether a drop of water missed a spot or whether they passed gas. The Prophet ﷺ dealt with this directly. A man complained about thinking he passed gas in prayer, and he was told not to leave unless he hears a sound or smells something (Sahih al-Bukhari 137). The ruling is firm on the side of not obsessing.