Certainty or conviction is a valuable capital which is given to only few people. Anybody possessing this, enjoys great prosperity.
Imam Reza (as) has stated:
"الاِيمانُ فَوقَ الاِسلامِ بِدَرَجَةٍ وَالتَقوَى فَوقَ الاِيمَانِ بِدَرَجَةٍ وَاليَقِينُ فَوقَ التَقوَى بِدَرَجَةٍ وَلَم يُقَسَّم بَينَ العِبَادِ شَيئٌ اَقَلُّ مِنَ اليَقِينُ"
"Faith is one degree above Islam; God-wariness is one degree above faith. Certainty is one degree above God-wariness. Nothing less than certainty is divided among God's believers"2
The narrator says: I heard Imam as-Sadiq (as) saying:
"اِنَّ العَمَلَ الدَائِمَ القَلِيلَ عَلى اليَقِين اَفضَلُ عِندَ الله مِنَ العَمَلِ الكَثِيرِ عَلى غَيرِ يَقِينٍ"
"Indeed, a small act based on certainty that is performed continually, is better before God than abundant actions not based on certainty"3
He also said:
"اِنَّ اللهَ بِعَدلِهِ وقِسْطِهِ جَعَلَ الرُّوحَ وَالرَّاحَة في اليَقِينَ وَالرِّضَا وَجَعَلَ الهَمَّ وَالحُزنَ في الشَّكِ وَالسَخَطِ"
"With his justice and fairness, God has put tranquility and ease in certainty and satisfaction, and has put sorrow and grief in doubt and displeasure".4
Notes:
2. Usul al-Kafi, vol. 2, pp.52-57.
3. Op cit.
4. Usul al-Kafi, vol.2, pp.52-57.