It is reported that Ibrāhīm b. Ad-ham – Allāh have mercy on him – said:

Zuhd (abstinence from materialism, asceticism) is of three types: (i) obligatory zuhd, (ii) virtuous zuhd and (iii) zuhd for safety. Obligatory zuhd is to abstain from what is forbidden (harām); virtuous zuhd is to be disinterested in what is allowed (of this world); and zuhd for safety is to stay away from doubtful matters.

Abū Bakr Al-Daynūrī, Al-Mujālasah wa Jawāhir Al-‘Ilm article 905.