I say, and with God's success: His wiping is invalidated; because it is not permissible to combine washing and wiping. Then it is considered: if he is not in a state of ritual impurity, he does not have to perform ablution, and washing his feet alone is sufficient, without washing the rest of the limbs. However, if he is in a state of ritual impurity, he must perform ablution; because the water touching the foot is not a real nullifier, but rather the nullifier is the previous state of impurity. However, when his foot became wet, the effect of the impurity appeared on the foot. See: Al-Maraqi p. 134, and Sharh Al-Wiqayah p. 117, and God knows best.