In his debate with the rafidi ibn Muttahar al-Hilli, shaykhul Islam ibn Taymiyyah said:
“You claim that Ali used to pray 1000 rakat every day and night. This is not true. Our prophet (sallalahu alaihi wa ala alihi wa sallam) wouldn’t pray at night more than 13 rakat. Also, it’s not recommended to pray all night; rather it’s disliked, because prophet (sallalahu alaihi wa ala alihi wa sallam) said to Amr ibn Al-As: “Your body has a right on you” (As it was recorded by Bukhari and others, he said it to Abu Darda). Furthermore, the prophet (sallalahu alaihi wa ala alihi wa sallam) used to pray about 40 rakat during the day and night. Ali’s knowledge of the prophet’s (sallalahu alaihi wa ala alihi wa sallam) sunnah, and his great concern to adhere to it, wouldn’t allow him to deviate from it – assuming that such deviation is possible. However, it’s impossible to pray 1000 rakat and still perform all his other obligations; he has obligations toward himself; the needs of sleep, food, drink, toilet, wudu, approaching his wives, looking after his family and subjects; etc., all of which would fill half of his time. In the remaining half, he should pray about eighty rakat per hour. One can’t pray eighty rakat in one hour unless it’s by reading Fatiha only, and without serenity. Ali is much better than to pray a prayer like that of the hypocrites, which is similar to the pecking of birds, and in which they seldom remember Allah – as is reported in two Saheehs”.
(“Al-Muntaqa min Minhaj il-itidaal” p 169-170, quoted from work by Muhammad al-Jibali “Qiyamul layl” pp 75-76)