It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Whoever seeks refuge with you in the name of Allah, give him refuge; whoever asks of you in the name of Allah, give to him; whoever invites you, accept his invitation; and whoever does you a kindness, repay him in full. If you find nothing with which to repay him, then praise him until you know that you have repaid him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7890