﴿ تُؤْمِنُونَ بِٱللَّهِ وَرَسُولِهِۦ وَتُجَٰهِدُونَ فِى سَبِيلِ ٱللَّهِ بِأَمْوَٰلِكُمْ وَأَنفُسِكُمْ ۚ ذَٰلِكُمْ خَيْرٌۭ لَّكُمْ إِن كُنتُمْ تَعْلَمُونَ ﴾

“You are to believe in God and His Apostle, and to strive hard in God's cause with your possessions and your lives: this is for your own good - if you but knew it!”

In trade, a man first invests and then receives a return on his investment. In the struggle for Faith also one has to invest his strength and his possessions. From this view point, this is also a sort of trade. But, one receives the profit from worldly trade in this world, while in the religion-oriented trade, one receives the profit with further additions only in the Hereafter.