Narrated Abu Ishaq:

Once, while I was sitting beside Zaid bin Al-Arqam, he was asked, "How many Ghazwat did the Prophet undertake?" Zaid replied, "Nineteen." They said, "In how many Ghazwat did you join him?" He replied, "Seventeen." I asked, "Which of these was the first?" He replied, "Al-'Ashira or Al-'Ashiru."

حَدَّثَنِي عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَهْبٌ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، كُنْتُ إِلَى جَنْبِ زَيْدِ بْنِ أَرْقَمَ، فَقِيلَ لَهُ كَمْ غَزَا النَّبِيُّ ﷺ مِنْ غَزْوَةٍ قَالَ تِسْعَ عَشْرَةَ. قِيلَ كَمْ غَزَوْتَ أَنْتَ مَعَهُ قَالَ سَبْعَ عَشْرَةَ. قُلْتُ فَأَيُّهُمْ كَانَتْ أَوَّلَ قَالَ الْعُسَيْرَةُ أَوِ الْعُشَيْرُ. فَذَكَرْتُ لِقَتَادَةَ فَقَالَ الْعُشَيْرُ.