Harms of Haram (illegal) livelihood
It is source of loss in this world and hereafter and it takes a person away from Allah's blessings which a person needs on every step.
The Holy Prophet said".
ثم ذكر الرَّجُلَ يُطِيلُ السَّفَرَ أَشْعَتَ أَغْبَرَ، يَدِيهِ إِلَى السَّمَاءِ يَارَبِّ وَمَطْعَمُهُ حَرَام وَمَشْرَبُهُ
جَرَاهُ، وَمَلْبَسُهُ حَرَامٌ، وَغُذِيَ بِالْحَرَامِ، فَأَنَّى يُسْتَجَابُ لِذلِكَ؟ (صیح مسلم :1015)
Translation: A person reaches kabah after a long journey. His hair is scattered and dusty. He catches the covering of Kabah and prays to Allah while shedding tears but his food, drinks is through haram (illegal) livelihood and dues also prepared from haram earnings, then how his prayer would be accepted.
Teachings of Prophets:
All Prophet's preached about legal earning halal and earned themselves the halal, legal livelihood. The best livelihood is that which is earned through work done by hands and Allah's Prophet Dawood used to earn through crafty work..
Condition for acceptance of worship:
It is must to earn through legal, halal means for the acceptance of worship. That person is forgiven whose body is nourished through halal means. Holy Prophet said, "Earn halal livelihood, your prayers will be accepted.
Training of Children:
It is vital for training of children to feed them through halal means otherwise there are very bad effects through wrong means of income. Parents should, feed them through legal. halal livelihood for making them good human beings.
All these teachings have deep philosophy in them. We should ponder it over how much important it is to earn through legal means. So It is very necessary to pay heed to eárn halal, legal, and to avoid haram, illegal income.