Ibn 'Umar reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Anyone who seeks refuge in Allah will find refuge with Him. Anyone who asks from Allah will be receive. Anyone who does a favour should repay it. If you do not find anything, then make supplication for the doer of the favour so that he knows that you have repaid him."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُسَدَّدٌ، قَالَ: حَدَّثَنَا أَبُو عَوَانَةَ، عَنِ الأَعْمَشِ، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عُمَرَ قَالَ: قَالَ رَسُولُ اللهِ صلى الله عليه وسلم: مَنِ اسْتَعَاذَ بِاللَّهِ فَأَعِيذُوهُ، وَمَنْ سَأَلَ بِاللَّهِ فَأَعْطُوهُ، وَمَنْ أَتَى إِلَيْكُمْ مَعْرُوفًا فَكَافِئُوهُ، فَإِنْ لَمْ تَجِدُوا فَادْعُوا لَهُ، حَتَّى يَعْلَمَ أَنْ قَدْ كَافَأْتُمُوهُ.
sunnah.com