Ibn 'Umar (May Allah be pleased with them) said:
The Messenger of Allah (ﷺ) said, "Grant shelter to him who begs for it in the Name of Allah, give to him who begs in the Name of Allah, accept the invitation of him who invites you, and requite him who does a favour to you, but if you are unable to requite him, go on praying for him till you are sure that you have requited him adequately."[Abu Dawud and An- Nasa'i].
App reference: Book 18, Hadith 213
Arabic/English book reference: Book 18, Hadith 1723