In the Futuhat Makkiyyah, Sayyadi Ibn Arabi, may Allah be Merciful to him, introduces the idea of Abu Yazid's perception of asceticism (Zuhd). He characterizes him as having stated that asceticism was an easy matter and that he had been an abstinent for 3 days.
On the 1st day he renounced this world (al-dunya)
On the 2nd day he renounced the world to come (al-akhira)
On the 3rd day he renounced everything which was not Allah.
Abu Yazid al-Bistami, may Allah be Merciful to him, was asked what he willed. He answered, "I will not to will, for I am the object of will (ana al-murad) and You (Allah) are the One who Wills (wa-anta al-murid)."-- meaning that renunciation of all things except Allah is the true meaning of asceticism.. Zuhd.