Musa b. Talha said he had the letter of Mu'adh b. Jabal from the Prophet (ﷺ) to the effect that he ordered him to collect <i>sadaqa</i> only on wheat, barley, raisins and dates. It is in mursal form and is transmitted in <i>Sharh as-sunna</i>.

وَعَنْ مُوسَى بْنِ طَلْحَةَ قَالَ: عِنْدَنَا كِتَابُ مُعَاذِ بْنِ جَبَلٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ قَالَ: إِنَّمَا أَمَرَهُ أَنْ يَأْخُذَ الصَّدَقَةَ مِنَ الْحِنْطَةِ وَالشَّعِيرِ وَالزَّبِيبِ وَالتَّمْرِ. مُرْسل رَوَاهُ فِي شرح السّنة