A Sin is any action that causes harm. Human techniques prevent what is apparent of sins. Such as the attempt to prevent robbery, assault, bribery, and so on, but Allah (swt) protects us from concealed sins. No doubt that the inward sins are more dangerous because they are the motivators of the outward sins as well as enmities. The concealed of sins include the diseases of the heart, such as grudge, animosity, envy, hatred, and so on. For example: envy causes enmities and breaks family bonds; and grudge leads to murder, and so on.
When societies follow the path of Allah (swt), they ensure thereby good life for people. For example, preventing people from stealing is a protection not only for one’s self, but is also a protection for others. Thus, Islam is the calling of goodness upon others. When Allah (swt) says in His Book:
وَقُولُوا لِلنَّاسِ حُسْنًا
(And speak to people good [words]) (Al-Baqara: 83)
إِنَّ اللَّهَ يَأْمُرُ بِالْعَدْلِ وَالْإِحْسَانِ وَإِيتَاءِ ذِي الْقُرْبَىٰ وَيَنْهَىٰ عَنِ الْفَحْشَاءِ وَالْمُنكَرِ وَالْبَغْيِ ۚ يَعِظُكُمْ لَعَلَّكُمْ تَذَكَّرُونَ
(Indeed, Allah orders justice and good conduct and giving to relatives and forbids immorality and bad conduct and oppression. He admonishes you that perhaps you will be reminded.) (An-Nahel:90)
All of these are for the better good of all mankind and not just Muslims.
( وَذَرُوا ظَاهِرَ الْإِثْمِ وَبَاطِنَهُ) (And leave what is apparent of sin and what is concealed thereof): Who watch what is concealed of sins? When we talk about morals, we say that they must be bound by religion. Morals cannot prevail without being connected with religion, that is because only religion can prevent what fights what is concealed of sins that cause bad behaviors. Realizing the fact that Allah (swt) is the only Watchful over our conscience and inner selves and that He (swt) is the All-Knowing of what is hidden in our hearts such as envy, hatred, gossip, or any similar matter, only then our morals will be straightened up accordingly.
However, if we were to say: “we want high morals, no doubt everyone loves morals, for that we will establish a law, for example, to protect properties and people against robbery, bribery embezzlement, cheating, deception …etc.” Nevertheless, this will not prevent what is concealed of sins. This is why Allah (swt) says:
( إِنَّ الَّذِينَ يَكْسِبُونَ الْإِثْمَ سَيُجْزَوْنَ بِمَا كَانُوا يَقْتَرِفُونَ) (Indeed, those who earn [blame for] sin will be recompensed for that which they used to commit). There is penalty on both the concealed, and the apparent of sins. Allah (swt) ensures that they will be punished for what they commit. He (swt) calls it (earning) which is committing both open and secret sins.