Salmān Al-Farisi (raḍiy Allāhu ʿanhu) in a few concise yet powerful words, says:
إِنَّ لِكُلِّ امْرِئٍ جُوَّانِيًّا [باطن]، وَبرَّانِيًّا [ظاهر]، فَمَنْ يُصْلِحُ جُوَّانِيَّهُ يُصْلِحُ اللَّهُ بَرَّانِيَّهُ وَمَنْ يُفْسِدُ جُوَّانِيَّهُ يُفْسِدُ اللَّهُ بَرَّانِيَّهُ
“Every person has an inner hidden affair and an outer public affair.
Whoever rectifies their inner affairs, Allāh will rectify their outer affairs.
And whosoever corrupts their inner affairs, Allāh will corrupt their out affairs.”