The Quranic basis for ablution before prayer is a single verse instructing believers to wash their faces and hands, wipe their heads, and wash their feet, along with a companion clause permitting dry ablution with clean earth when water cannot be found or used. Everything beyond that spare instruction, the order of the steps, how much of the arm counts as included, whether the ears are washed with the head or separately, what specifically breaks a completed wudu, was worked out over the following centuries by jurists building the classical legal schools, and the four surviving Sunni schools do not agree on every point.
Whether touching a woman invalidates ablution, whether bleeding does, and whether wiping over socks is permitted, and for how long, are live disagreements among the schools rather than settled Quranic rulings, and a Muslim traveling between regions can find the accepted practice varies. Tayammum, the dry substitute using earth or a clean surface, was itself controversial early on: some companions reportedly hesitated to use it at all, preferring to delay prayer until water was found, before the practice was accepted as fully sufficient rather than a lesser option. The five daily prayers require the ablution to be repeated whenever it has lapsed, which is why sequence and validity receive so much more juristic attention than the act's outward form.