What is the ruling on washing the feet in ablution, and do the Qur'anic verses permit wiping over them, or wiping over socks?

Washing the shins is not obligatory in ablution (wudu') because Allah Almighty specified the limit for washing the feet as the ankles in His saying: (and your feet to the ankles). However, it is recommended to wash part of the shins as a way of increasing reward, due to the Prophet's (peace and blessings be upon him) saying: "Indeed, my nation will be called on the Day of Resurrection 'ghurran muhajjaleen' (white-faced and with white streaks on their limbs) from the traces of ablution." Scholars have differed on the recommended extent of lengthening the 'tahjeel' (white streaks on the limbs), and the correct view is that it is sunnah to lengthen both the 'ghurrah' (white-faced) and the 'tahjeel' according to one's ability.