Buraydah ibn al-Hasib

Buraydah ibn al-Ḥaṣīb was a Companion the Prophet (ﷺ) sent, disguised as an unaffiliated Bedouin, to confirm reports that al-Ḥārith ibn Abī Ḍirār, chieftain of Banū al-Muṣṭaliq, was preparing to attack Madinah. Posing as a mercenary seeking a share of any plunder, Buraydah gained al-Ḥārith's confidence, confirmed the plan was genuine, and slipped away at night to report back, allowing the Prophet (ﷺ) to launch a decisive pre-emptive strike before Banū al-Muṣṭaliq had any warning.