Is it obligatory to touch all the parts of the body involved in ablution during the process, or is it sufficient for the water to reach them?

The majority of scholars (Hanafi, Shafi'i, and Hanbali schools) are of the opinion that rubbing the limbs during ablution is a Sunnah, not an obligation, unlike the Maliki school who consider it obligatory. The evidence for the majority is the saying of the Prophet, peace and blessings be upon him: "If you find water, let it touch your skin." However, if the water does not reach the skin except by rubbing, then it becomes obligatory.