It is claimed by some that the expedition of Shuja ibn Wahb al-Asadi took place as a result that the Muslims wanted to steal stuff from the Banu Amir tribe.
However, this not true. It is reported in our Islamic sources that one of the reasons Companions of the Prophet (p) were despatched, was a result of this enemy who had made preparations in planning to attack the Muslim community.
Kitab Al-tabaqat Al-Kabir – Ibn Sa’d:
“THE SARIYYAH OF SHUJA IBN WAHB AL-ASADI AGAINST BANU AMIR AT AL-SIYYI
Then (occurred) the saruyyah of Shuja Ibn Wahb al-Asadi against Banu Amir at al-Siyyi in the month of Rabi al-Awwal of the eight year from the hijrah of the Apostle of Allah. Muhammad Ibn Umar al-Aslami informed us:
Abu Bakr Ibn Abd Allah Ibn Abi Sabrah related to me on the authority of Ishaq Ibn Abd Allah Ibn Abi Farwah, he on the authority of Umar Ibn al-Hakam, he said:
The Apostle of Allah sent Shuja Ibn Wahb with twenty four persons, to a CONCENTRATION OF THE HAWAZIN at al-Siyyi in the territory of Rukbah beyond al-Madinah. It lies at (a distance of) five nights journey from al-Madinah.
He (Prophet) ordered him to attack them. He marched in the night and remained in concealment in the dayl it was one morning when they attacked them. … The warriors had remained absent for fifteen days.” 
“THE EXPEDITION OF SHUJA B. WAHB TO AL SIYY
… The Messenger of God sent Shuja b. Wahb with twenty-four men to a GATHERING OF THE HAWAZIN in al-Siyy. The Messenger of God commanded him to attack them. So he set out.
He used to march by night and hide by day until he attacked them one morning when they were careless. He had informed his companions before that, that they should not be excessive in the serach. … The expedition lasted fifteen nights.“ 
Mohammad Khalid parwej:
“In Madinah he was paired with Aws Ibn Khaula. He took part in all the battles which the Muslims fought with the Quraysh. He played a prominent role in an expedition which was sent to deal with the Banu Hawazin who had camped at Afgan (located at some distance from Madinah) with the intention of attacking the Muslims. Shuja ibn Wahab, along with twenty-four other companions, went there, fought with the Banu Hawazin and overpowered them. …” 
 Kitab Al-tabaqat Al-Kabir, by Ibn Sa’d, volume 2 – Page 157
 The Life of Muhammad: Al-Waqidi’s Kitab Al-Maghazi [Translator: Rizwi Faizer], volume 2, page 371
 365 days with sahabah By Mohammad Khalid parwej, page 194