Sahih Bukhari

Narrated Abu 'Is-haq: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