The Prophet ﷺ said: If anyone seeks protection in Allah's name, grant him protection; if anyone begs in Allah's name, give him something; if anyone gives you an invitation, accept it; and if anyone does you a kindness, recompense him; but if you have not the means to do so, pray for him until you feel that you have compensated him. (Using translation from Abū Dāʾūd 1672)   

أَنَّ النَّبِيَّ ﷺ قَالَ مَنِ اسْتَعَاذَكُمْ بِاللهِ فَأَعِيذُوهُ وَمَنْ سَأَلَكُمْ بِاللهِ فَأَعْطُوهُ وَمَنْ دَعَاكُمْ فَأَجِيبُوهُ وَمَنْ أَتَى إِلَيْكُمْ مَعْرُوفًا فَكَافِئُوهُ فَإِنْ لَمْ تَجِدُوا مَا تُكَافِئُونَهُ بِهِ فَأَثْنُوا عَلَيْهِ حَتَّى تَعْلَمُوا أَنَّكُمْ قَدْ كَافَأْتُمُوهُ