Raisins were steeped for the Messenger of Allah ﷺ and then dried dates were infused in them, or dried dates were steeped and then raisins were infused in them.
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُنْبَذُ لَهُ زَبِيبٌ فَيُلْقِي فِيهِ تَمْرًا وَتَمْرٌ فَيُلْقِي فِيهِ الزَّبِيبَ