That He might cut off a fringe of the Unbelievers or expose them to infamy, and they should then be turned back, frustrated of their purpose.
The words “Allah has made it but a message of hope” refer to the promise of victory mentioned in the above verse. In other words, the special promise of help through angels on this occasion was given only as good news to you and to remove your dismay caused by the hostility of your enemies and the treacherous behaviour of the hypocrites. For, even if such a glad tiding was not revealed, the believers should always firmly believe that victory and success lies only in the hands of Allah. He is mighty and supreme as well wise, and as such none of His acts is without wisdom behind it.
The sentence “li-yaqṭa-‘ a ṭarafan minalladhīna kafarū…( that He might cut off a portion of the unbelievers …”) explains the purpose of specially encouraging the believers and the decision of Allah that the Quraysh would either be crushed in this battle or be beaten back with humiliation or at least, lose a portion of their strength.
Islahi, Amin Ahsan. Pondering Over The Qur’an: Surah Ali Imran (p. 237). Islamic Book Trust. Kindle Edition.