Hasan ibn Ali

The Expeditions of Yemen () were the 7th-century campaigns of Ali in South Arabia.
Campaigns.
In December 631 (10 AH), Muhammad dispatched his close companion Ali with 200–300 troops to an expedition into Yemen. Muhammad instructed Ali not to engage the enemies until they attack. 
Ali sent out his men, they obtained spoils of war, women, children, camels and flock. Once he met with the people, he invited them to Islam. They rejected him and launched an attack with arrows and rocks. Ali and his men then charged back at them and killed 20 of their men, so they fled. Ali held back the army from pursuing the fleeing enemy and invited them once more to Islam. They quickly responded and pledged allegiance to him. The tribe did this quickly and submitted themselves to Muʿādh ibn Jabal, Muhammad's envoy in Yemen.
Aftermath.
According to Sunni Islam, Muhammad honored Ali for his campaigns in Yemen in March 632 (Dhu al-Hijja 10 AH). He said "He whose "mawla" I am, Ali is his "mawla"".