Expedition of Dhul-Qassah
The Holy Prophet (sa) sent Hazrat Abu Ubaidah bin Jarrah (ra) on many saraya – saraya is the plural of sariyah, meaning battles or expeditions.
He was sent on the expedition of Dhul-Qassah in Rabi‘-ul-Akhir, 7 AH. In relation to this, Hazrat Mirza Bashir Ahmad MA (ra) writes in Sirat Khatamun-Nabiyyin:
“In the month of Rabi‘-ul-Akhir, the Holy Prophet (sa) sent Muhammad bin Maslamah Ansari (ra) to Dhul-Qassah which was located at a distance of 24 miles from Medina, where, in those days, the Banu Tha‘labah resided. When Hazrat Muhammad bin Maslamah(ra) and his 10 companions reached there at night they found 100 young tribesmen prepared for battle. This party was 10 times the numerical value of the companions … Muhammad bin Maslamah (ra) immediately marshalled his troops before the army (if they went with the intention of war, they would never have gone with so few numbers) and there was a war of archery throughout the darkness of the night. After this, the disbelievers marched forward to attack this handful of men and since they were much greater in number, it was not long before these 10 devotees of Islam fell to the ground (i.e. they were martyred). The companions of Muhammad bin Maslamah (ra) were all martyred, but Muhammad bin Maslamah (ra) himself survived, because the disbelievers had left him with the others, thinking he had also perished and stripped him of his clothes. Perhaps Muhammad bin Maslamah (ra) would have died lying there as well, but fortunately, a Muslim passed by and recognising Muhammad bin Maslamah (ra), picked him up and took him to Medina.
When the Holy Prophet (sa) was informed of these events, he sent Abu Ubaidah bin Jarrah (ra) who was from the Quraish and was counted among the preeminent of companions to Dhul-Qassah, to seek retribution for Muhammad bin Maslamah (ra). Moreover, since news had also been received that the people of the Banu Tha‘labah tribe intended to attack the surroundings of Medina, the Holy Prophet (sa) sent a party of 40 adept companions under the command of Abu Ubaidah (ra). The Holy Prophet (sa) ordered that they travel by night and reach there in the morning. In the fulfilment of this order, Abu Ubaidah (ra) reached there punctually with his forces, when it was time for the morning prayer. The enemy were confused by this sudden attack and so after a brief confrontation, they fled, disappearing to the nearby mountains. Abu Ubaidah (ra) took hold of the spoils of war and returned to Medina.”
(Sirat Khatamun-Nabiyyin, Hazrat Mirza Bashir Ahmad (ra), p. 668)
This expedition was sent to seek retribution against the injustice or perhaps to punish them for their crime.