The three initial washings of the hands and the obligatory washing of the arms are distinct in purpose.
If someone omits the separate opening washings but later washes hands and arms correctly up to and including the elbows, the fard is fulfilled, although the initial sunnah was missed. This keeps the completion of a fard separate from the completion of the sunnah sequence.
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Sunnahs of Wudu and Their Juristic Rulings
The three initial washings of the hands and the obligatory washing of the arms are distinct in purpose.
If someone omits the separate opening washings but later washes hands and arms correctly up to and including the elbows, the fard is fulfilled, although the initial sunnah was missed. This keeps the completion of a fard separate from the completion of the sunnah sequence.