The following is taken from the Quranic exegesis of Sahl al-Tustari (r.a).
Imam Tustari (r.a) explained that it means, ‘You will not attain full mindfulness of God until you go to war with your lo- wer selves and expend some of what you love.’ Furthermore, there is no spending (infaq) like consuming (infaq) the lower self by opposing it, and by seeking the good pleasure of God, Mighty and Majestic is He.
Then he related a story of Jesus (a.s):
Once Jesus (a.s) passed by three people whose bodies were emaciated and faces pale. He (a.s) asked them, ‘What has brought- you to this state I see you in?’ They said, ‘The fear (khawf) of our Creator and wariness (hadhr) of punishment for our disobedience.’ He (a.s) responded, ‘God made it incumbent upon Himself to grant safety to the one who fears [Him].’ Then he (a.s) moved on until he (a.s) came to three other people who were even more emaciated. He (a.s) asked them, ‘What has brought you to this state I see you in?’ They answered, ‘The yearning (shawq) for our Lord.’ He (a.s) replied, ‘God made it incumbent upon Himself to grant you what you wish for.’ Then he (a.s) moved on until he (a.s) came to three people who were even more emaciated, whose faces were like full moons. He (a.s) asked, ‘What has brought you to this state I see you in?’ They replied: ‘Love (hubb).’ He (a.s) said, ‘You are the people of proximity [with God] (muqarrabun)’, and he (a.s) said it thrice. Thus,whoever loves God, Exalted is He, is one of the people of proximity [with God], for if anyone loves something they hasten towards it. So the first level is the rank of the repentant (tawwabun); the second is that of the people of longing (mushtaqun), and then the servant reaches the third rank which is that of love. Do you not see how they gave their all for the sake of the One who possesses all, turned their backs on all, and faced the direction of the One who possesses all?