وَمَا كَانَ أَكْثَرُ نَصَبًا وَأَفْضَلُ نَفَقَةً فَالْأَجْرُ عَلَى قَدْرِ النَّصَبِ وَالنَّفَقَةِ.
Because there is more hardship and expense in it. The more hardship you endure and the more wealth you spend in the way of Allah, the greater will be the reward and recompense.