Whether a source of income is lawful or unlawful is governed by the specific rulings on business transactions. In the case mentioned, even if every business ruling has been observed, the income earned from it will be ill-omened and without blessing, because it involves insulting the sacred station of the Friends of God, His Proofs, and His vicegerents on earth. The following noble verses show the way forward:
al-Nisāʾ 4:97 إِنَّ الَّذينَ تَوَفَّاهُمُ الْمَلائِكَةُ ظالِمي أَنْفُسِهِمْ قالُوا فيمَ كُنْتُمْ قالُوا كُنَّا مُسْتَضْعَفينَ فِي الْأَرْضِ قالُوا أَ لَمْ تَكُنْ أَرْضُ اللَّهِ واسِعَةً فَتُهاجِرُوا فيها فَأُولئِكَ مَأْواهُمْ جَهَنَّمُ وَ ساءَتْ مَصيراً
When the angels take the souls of those who have wronged themselves, they ask, “What were you doing?” (Why, when you were Muslims, did you remain among the disbelievers?) They reply, “We were oppressed and helpless in our land.” The angels say, “Was God’s earth not vast enough for you to migrate?” Such people have no excuse; their abode is Hell—an evil destination.
al-ʿAnkabūt 29:56 or عِبادِيَ الَّذينَ آمَنُوا إِنَّ أَرْضي واسِعَةٌ فَإِيَّايَ فَاعْبُدُونِ
O My servants who believe! My earth is vast, so worship Me alone!
al-Zumar 39:10 قُلْ يا عِبادِ الَّذينَ آمَنُوا اتَّقُوا رَبَّكُمْ لِلَّذينَ أَحْسَنُوا في هذِهِ الدُّنْيا حَسَنَةٌ وَ أَرْضُ اللَّهِ واسِعَةٌ إِنَّما يُوَفَّى الصَّابِرُونَ أَجْرَهُمْ بِغَيْرِ حِسابٍ
Say, “O My servants who believe! Be mindful of your Lord. Those who do good in this world will have a good reward. God’s earth is vast; those who are patient will be given their reward without measure!”
al-Tawbah 9:24 قُلْ إِنْ كانَ آباؤُكُمْ وَ أَبْناؤُكُمْ وَ إِخْوانُكُمْ وَ أَزْواجُكُمْ وَ عَشيرَتُكُمْ وَ أَمْوالٌ اقْتَرَفْتُمُوها وَ تِجارَةٌ تَخْشَوْنَ كَسادَها وَ مَساكِنُ تَرْضَوْنَها أَحَبَّ إِلَيْكُمْ مِنَ اللَّهِ وَ رَسُولِهِ وَ جِهادٍ في سَبيلِهِ فَتَرَبَّصُوا حَتَّى يَأْتِيَ اللَّهُ بِأَمْرِهِ وَ اللَّهُ لا يَهْدِي الْقَوْمَ الْفاسِقينَ
Say, “If your fathers, your sons, your brothers, your spouses, your clan, the wealth you have acquired, the trade whose decline you fear, and the homes you cherish are dearer to you than God, His Messenger, and striving in His way, then wait until God brings about His command. God does not guide a disobedient people.”