The implicit arguments are the ‘Aql’ (intellect). يَا هِشَامُ إِنَّ الْعَاقِلَ الَّذِي لَا يَشْغَلُ الْحَلَالُ شُكْرَهُ وَ لَا يَغْلِبُ الْحَرَامُ صَبْرَهُ O Hisham! The (possessor of) the (true) Aql is the one who is not diverted from thanking Allah -azwj after obtaining the permissible provisions and observes patience/abstinence from the non-permissible means.
يَا هِشَامُ كَيْفَ يَزْكُو عِنْدَ اللَّهِ عَمَلُكَ وَ أَنْتَ قَدْ شَغَلْتَ عَقْلَكَ عَنْ أَمْرِ رَبِّكَ وَ أَطَعْتَ هَوَاكَ عَلَى غَلَبَةِ عَقْلِك O Hisham! How come do you expect that Allah -azwj will accept your deeds while you are involving your Aql with matters that are away from Allah -azwj ’s Commandments and you are complying with your ‘هَوَاكَ’ ‘desires’ and letting them to overcome your Aql.
The Aql is the (quality) through which the Commandments of Allah -azwj are understood and will surely withdraw from the people of the worldly pleasures. He (due to Aql) will also be inclined towards that which Allah -azwj has Promised and will regard Allah -azwj as refuge in his solitude (loneliness), the companion in loneliness, the fortune in poverty and the supporter instead of the clan.
َ يَا هِشَامُ إِنَّ الْعُقَلَاءَ تَرَكُوا فُضُولَ الدُّنْيَا فَكَيْفَ الذُّنُوبُ وَ تَرْكُ الدُّنْيَا مِنَ الْفَضْلِ وَ تَرْكُ الذُّنُوبِ مِنَ الْفَرْضِ O Hisham! The ones with Aql have left the pleasures of this world. How is it then for the sins? The abstinence from the worldly pleasures is recommendable while avoidance of committing sins is obligatory. يَا هِشَامُ كَانَ أَمِيرُ الْمُؤْمِنِينَ ع يَقُولُ مَا مِنْ شَيْءٍ عُبِدَ اللَّهُ بِهِ أَفْضَلَ مِنَ الْعَقْل O Hisham!
Amir-ul-Momineen -asws used to say: The most elevated means of worshiping Allah -azwj is making use of Aql. ً يَا هِشَامُ اعْرِفْ الْعَقْلَ وَ جُنْدَهُ وَ الْجَهْلَ وَ جُنْدَهُ تَكُنْ مِنَ الْمُهْتَدِين O Hisham! Recognise the armies of the Aql and the armies of the ‘Jahil’ (opposite of Aql) and you will be guided.