Sahl on Spirituality: Four qualities which make a saint

Abu Talib al-Makki reported: Sahl al-Tustari, may Allah have mercy on him, said, “All good is combined in these four traits, and by them the righteous replacements (al-abdal) became replacements: having slender bellies, silence, sleeplessness, and withdrawing from people.”

Source: Qūt al-Qulūb 1/170

عن أبي طالب المكي قَالَ سَهْلٌ التُّسْتَرِيُّ رحمه الله اجتمع الخير كله في هذه الأربع خصال وبها صار الإبدال إبدالاً إخماص البطون والصمت والسهر والاعتزال عن الناس

1/170 قوت القلوب في معاملة المحبوب