[Remember] when He overwhelmed you with drowsiness [giving] security from Him and (8:11)

Almuntakhab Fi Tafsir Alquran Alkarim

And there did Allah replace the emotion of sorrow and grief which was caused by fear of the unpredictable outcome by peace of mind and sense of security thus inducing your eyes to take themselves to slumber. He sent down from the floor of the vault of heaven rain - water to free you people from foreign matter as well as from moral and spiritual pollution and from the incitement of evil instigated by AL-Shaytan (Satan) and by those with characteristics befitting Him, and to do your hearts good and set your feet firm

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(8:11) And recall when Allah brought on you drowsiness, *8 giving you a feeling of peace and security from Him, and He sent down rain upon you from the sky that He might cleanse you through it and take away from you the pollution of Satan and strengthen your hearts, and steady your feet through it. *9

[Remember] when He overwhelmed you with drowsiness [giving] security from Him and meaning

*8). In the Battle of Uhud the Muslims passed through a similar experience (see Al'lmran 3: 154 above). On both occasions, when prevalent conditions should have produced intense fear and panic among them, God filled their hearts with such peace and tranquillity that they were overpowered with drowsiness.
*9). This refers to the heavy downpour on the night preceding the Battle of Badr. It helped the Muslims in three ways. First, it provided them with an abundant water supply which they quickly stored in large reservoirs. Second, rain compacted the loose sand in the upper part of the valley where the Muslims had pitched their tents. This helped the Muslims plant their feet firmly and facilitated their movement. Third, where the Quray'sh army was stationed in the lower part of the valley, the ground turned marshy.
The defilement caused by Satan which occurs in the verse refers to the fear and panic which initially, afflicted the Muslims.
 

[Remember] when He overwhelmed you with drowsiness [giving] security from Him and meaning in Urdu

اور وہ وقت جبکہ اللہ اپنی طرف سے غنودگی کی شکل میں تم پر اطمینان و بے خوفی کی کیفیت طاری کر رہا تھا، اور آسمان سے تمہارے اوپر پانی برسا رہا تھا تاکہ تمہیں پاک کرے اور تم سے شیطان کی ڈالی ہوئی نجاست دُور کرے اور تمہاری ہمت بندھائے اور اس کے ذریعہ سے تمہارے قدم جما دے