48:18

(48:18) Allah was pleased with those who immunize when they swore to you under the Tree. He knew what was in their hearts, and sent down for them the Tranquility, and rewarded them with a close fitting

Connected

(48:4) He is the One who sends down the Tranquility into the hearts of those who acknowledge, so that they may increase in acknowledgement along with their present acknowledgement. To God belongs the soldiers of the heavens and the earth, and God is knowledgeable, wise.