That the Messenger of Allah (ﷺ) advanced towards Badr till he reached Harrah Al-Wabr where he was met by a man from the idolaters, about whom it was said he was brave and courageous. The Prophet (ﷺ) said to him: "Do you believe in Allah and his Messenger?" He said: "No." He said: "Then return, because we do not seek aid from an idolater."

The Hadith has more dialogue than this. And this is a Hasan Gharib Hadith. This is acted upon according to some of the people of knowledge. They say that the people of Adh-Dhimmah do not recieve a share, even it they were to fight along with the Muslims against the enemy.

Some of the people of knowledge said that they are given a share when they attend the battle with the Muslims.