It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever asks you in the name of Allah, give to him; whoever invites you, accept his invitation; whoever gives you a gift, return something in exchange for it, and if you do not find anything to give in return, then pray for him so much that you feel certain you have repaid him."