Imam Abul’ Abbas al-Qurtubi al-Maliki {May Allah have mercy upon him} said:
“The Sahaba and those that followed them would persevere with the Sunan {voluntary deeds} and Fada’il {virtuous deeds} just as they would with the Fara’id {obligatory matters} aiming to maximize their reward therein.
It was only the Jurists {Fuqaha} who differentiated between these two classes of action {obligatory and non-obligatory} because of subsequent legal matters such as the necessity of repeating certain actions, or the fear of punishment if such an action was abandoned etc.”
{al-Mufhim fi Sharh Mukhtasar Muslim}