SURAH AL-E-IMRAN: 121-122

TRANSLATION:

[3:121]
Recall the time when you left your house in the morning in order to place the believers in positions for fighting. {40} Allah is All-Hearing, All-Knowing.
[3:122]
When two of your groups were about to lose heart, {41} while Allah was their guardian! It is in Allah alone that the believers must place their trust.

INTERPRETATION:

{40} In Ghazvah Uhud (Ghazvat are those wars Muslims fought in which the Holy Prophet ﷺ himself took part) an army of three thousand non-believers from Meccah had attacked Medinah. The Holy Prophet ﷺ had taken Muslims to the plain next to the Uhud mountain to fight them. The next few verses make references to a number of incidents that took place during that battle. 

{41} When the Holy prophet ﷺ left Medinah to fight the non-believers he was accompanied by one thousand men. However, the leader of the Hypocrites, Abdullah Ibn Ubbi, deserted them with his three hundred men while on the way, saying that their recommendation was that they should fight the non-believers from within Medinah. As the Holy Prophet ﷺ had come out of Medinah against his recommendation he and his men would not join the battle. Upon seeing two other tribes of true Muslims, Banu Harthah and Banu Salmah, also became ambivalent and thought that seven hundred men were too few to fight three thousand men, therefore, they should also not join the battle. However, Allah Ta’alah helped them and they joined the battle. In this verse, there is a reference to these two tribes.