Hadith 1455
It is narrated from Abu Ghatfan bin Tarif that Sayyiduna Umar bin Khattab (may Allah be pleased with him) said: Whoever gives a gift to a relative for the sake of maintaining family ties, or as charity for the sake of reward, then he cannot take it back. And whoever gives a gift in exchange for something, then he can take it back if he becomes displeased.
Hadith 1455B1
قَالَ يَحْيَى : سَمِعْتُ مَالِكًا، يَقُولُ : الْأَمْرُ الْمُجْتَمَعُ عَلَيْهِ عِنْدَنَا أَنَّ الْهِبَةَ إِذَا تَغَيَّرَتْ عِنْدَ الْمَوْهُوبِ لَهُ لِلثَّوَابِ بِزِيَادَةٍ أَوْ نُقْصَانٍ، فَإِنَّ عَلَى الْمَوْهُوبِ لَهُ أَنْ يُعْطِيَ صَاحِبَهَا قِيمَتَهَا يَوْمَ قَبَضَهَا
Imam Malik, may Allah have mercy on him, said: In our view, this ruling is agreed upon that when there is some difference in the gifted item due to increase or decrease, and the gift is such that it was given in exchange for something, then the recipient of the gift will have to pay its price according to the day it was taken into possession.