Muwatta Imam Malik Book of Judgements, Hadith 42

Malik related to me from Da'ud ibn al-Husayn from Abu Ghatafan ibn Tarif al-Muriyi that Umar ibn al-Khattab said, "If someone gives a gift to strengthen ties with a relative or as sadaqa, he cannot have it returned. If some one, however, gives a gift seeking by it favour or reward, he has his gift and can reclaim it if he does not have satisfaction from it."
Yahya said that he heard Malik say, "The generally agreed-on way of doing things in our community is that if the gift is returned to the one who gave it for recompense, and its value has been either increased or decreased, the one to whom it has been given gives the owner its value on the day he received it."

حَدَّثَنِي مَالِكٌ، عَنْ دَاوُدَ بْنِ الْحُصَيْنِ، عَنْ أَبِي غَطَفَانَ بْنِ طَرِيفٍ الْمُرِّيِّ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ مَنْ وَهَبَ هِبَةً لِصِلَةِ رَحِمٍ أَوْ عَلَى وَجْهِ صَدَقَةٍ فَإِنَّهُ لاَ يَرْجِعُ فِيهَا وَمَنْ وَهَبَ هِبَةً يَرَى أَنَّهُ إِنَّمَا أَرَادَ بِهَا الثَّوَابَ فَهُوَ عَلَى هِبَتِهِ يَرْجِعُ فِيهَا إِذَا لَمْ يُرْضَ مِنْهَا . قَالَ يَحْيَى سَمِعْتُ مَالِكًا يَقُولُ الأَمْرُ الْمُجْتَمَعُ عَلَيْهِ عِنْدَنَا أَنَّ الْهِبَةَ إِذَا تَغَيَّرَتْ عِنْدَ الْمَوْهُوبِ لَهُ لِلثَّوَابِ بِزِيَادَةٍ أَوْ نُقْصَانٍ فَإِنَّ عَلَى الْمَوْهُوبِ لَهُ أَنْ يُعْطِيَ صَاحِبَهَا قِيمَتَهَا يَوْمَ قَبَضَهَا .