People used to give some of their datepalms to the Prophet (as a gift), till he conquered Bani Quraiza and Bani An-Nadir, whereupon he started returning their favors.
سَمِعْتُ أَنَسَ بْنَ مَالِكٍ ؓ يَقُولُ كَانَ الرَّجُلُ يَجْعَلُ لِلنَّبِيِّ ﷺ النَّخَلاَتِ حَتَّى افْتَتَحَ قُرَيْظَةَ وَالنَّضِيرَ فَكَانَ بَعْدَ ذَلِكَ يَرُدُّ عَلَيْهِمْ