Translation:

249. When Talut set forth with the armies he said: "Allah will test you at the stream; if any drinks of its water he goes not with my army; only those who taste not of it go with me; a mere sip out of the hand is excused." But they all drank of it except a few. When they crossed the river he and the faithful ones with him they said: "This day we cannot cope with Goliath and his forces." But those who were convinced that they must meet Allah said: "How oft by Allah's will hath a small force vanquished a big one? Allah is with those who steadfastly persevere."

Notes (Tafseer)

284. A Commander is hampered by a large force if it is not in perfect discipline and does not whole-heartedly believe in its Commander. He must get rid of all the doubtful ones, as did Gideon before Saul, and Henry V. in Shakespeare's story long afterwards. Saul used the same test as Gideon; he gave a certain order when crossing a stream; the greater part disobeyed, and were sent back. Gideon's story will be found in Judges, vii. 2-7.

285. Even in the small band that remained faithful, there were some who were appalled by the number of the enemy when they met him face to face, and saw the size and strength of the enemy Commander, the giant Goliath (Jalut). But there was a very small band who were determined to face all odds because they had perfect confidence in God and in the cause for which they were fighting. They were for making a firm stand and seeking God's help. Of that number was David; see next note.