Surely Allah has pleased towards the believers when they were pledging to you under the tree; then He knew what is in their hearts, then he sent down tranquility upon them, and He rewarded them a nearby Victory.
The pledge mentioned in this verse refers the pledge done by the believers from under a tree at ‘Hudaibiya’ declaring that they were ready for anything in the way of Allah including martyrdom as explained in verse 10 of this Surah. Then Allah increased their belief and sent down peace and tranquility to them just like he increased Guidance to the companions of the cave as mentioned in verse 18: 13. ‘The nearby Victory’ mentioned in this verse refers ‘the Maccan Victory’ happened in the 8th of Hijra. See explanation 5: 119; 33: 35; and 48: 4.