'Aa-sim bin Damrah Radiyallahu'Anhu says: "We asked'Ali about the nawaafil that Rasulullah Sallallahu 'Alayhi Wasallam performed in the day". (He must have known already about the nawaafil of the night i.e. tahajjud etc. Many well known narrations have been narrated regarding the tahajiud) 'Ali Radiyallahu 'Anhu replied: "You do not have the strength to perform these."
(i.e. The importance, punctuality, humility and humbleness Sayyidina Rasulullah Sallallahu 'Alayhi Wasallam attached to performing these prayers, cannot be fulfilled. The reason for saying this was to admonish, as what benefit is there simply by asking and investigating, until an effort is not made to practise these) We replied: "The one amongst us who has the strength, will perform it"., (Those who do not possess the strength, will learn so that others could be guided
and an effort will be made to practise). 'Ali Radiyallahu 'Anhu said: "In the morning when the sun rises to the height of that, the same as it is at the time for 'asr. At that time Rasulullah Sallallahu 'Alayhi Wasallam performed two rak'ahs (Salaatul ish-raaq). When the sun rose in the east to the height, where it is in the west at the time of zuhr salaah, he performed four rak'ahs (salaatut duha-chaast-, this will be explained in the ensuing chapter). He performed four rak'ahs before the salaah of zuhr, and two.after (These six rak'ahs are sunnah mu-akkidah). Four rak'ahs were performed before 'asr. In between the four rak'ahs he sat and sent salutations on the malaaikah.muqarrabeen, the ammbiyaa and the mu-mineen".