Maghrib and 'Isha'. Another opinion relates it to Tahsyjud Salaat.
Ma'az Radhiallaho anho has quoted Rasulullah Sallallaho alaihe
wasallam as saying that this Ayat refers to standing up at night
Another Hadith, quoted by Mujahid Rahmatullah Alaihe, says that
Rasulullah Sallallaho alaihe wasallam talked about standing in
Salaat at night and tears rolled down from his eyes.