Qur'an
Surah 2 2:249
فَلَمَّا فَصَلَ طَالُوتُ بِٱلۡجُنُودِ قَالَ إِنَّ ٱللَّهَ مُبۡتَلِیكُم بِنَهَرࣲ فَمَن شَرِبَ مِنۡهُ فَلَیۡسَ مِنِّی وَمَن لَّمۡ یَطۡعَمۡهُ فَإِنَّهُۥ مِنِّیۤ إِلَّا مَنِ ٱغۡتَرَفَ غُرۡفَةَۢ بِیَدِهِۦۚ فَشَرِبُوا۟ مِنۡهُ إِلَّا قَلِیلࣰا مِّنۡهُمۡۚ فَلَمَّا جَاوَزَهُۥ هُوَ وَٱلَّذِینَ ءَامَنُوا۟ مَعَهُۥ قَالُوا۟ لَا طَاقَةَ لَنَا ٱلۡیَوۡمَ بِجَالُوتَ وَجُنُودِهِۦۚ قَالَ ٱلَّذِینَ یَظُنُّونَ أَنَّهُم مُّلَـٰقُوا۟ ٱللَّهِ كَم مِّن فِئَةࣲ قَلِیلَةٍ غَلَبَتۡ فِئَةࣰ كَثِیرَةَۢ بِإِذۡنِ ٱللَّهِۗ وَٱللَّهُ مَعَ ٱلصَّـٰبِرِینَ ۝٢٤٩
When Talut set out with his forces, he said to them, ‘God will test you with a river. Anyone who drinks from it will not belong with me, but anyone who refrains from tasting it will belong with me; if he scoops up just one handful [he will be excused].’ But they all drank [deep] from it, except for a few. When he crossed it with those who had kept faith, they said, ‘We have no strength today against Goliath and his warriors.’ But those who knew that they were going to meet their Lord said, ‘How often a small force has defeated a large army with God’s permission! God is with those who are steadfast.’

Allah states that Talut, the king of the Children of Israel, marched forth with his soldiers and the Israelites who obeyed him. His army was of eighty thousand then, according to As-Suddi, but Allah knows best. Talut said:
إِنَّ اللَّهَ مُبْتَلِيكُم
(Verily, Allah will try you) meaning, He will test you with a river, which flowed between Jordan and Palestine, i.e. , the Shari`ah river, according to Ibn `Abbas and others. He continued,
فَمَن شَرِبَ مِنْهُ فَلَيْسَ مِنِّي
(So whoever drinks thereof, he is not of me;) meaning, shall not accompany me today,
لَّمْ يَطْعَمْهُ فَإِنَّهُ مِنِّى إِلاَّ مَنِ اغْتَرَفَ غُرْفَةً بِيَدِهِ
(and whoever tastes it not, he is of me, except him who takes (thereof) in the hollow of his hand.) meaning, there is no harm in this case. Allah then said:
فَشَرِبُواْ مِنْهُ إِلاَّ قَلِيلاً مِّنْهُمْ
(Yet, they drank thereof, all, except a few of them.)
Ibn Jurayj stated that Ibn `Abbas commented, "Whoever took some of it (the river's water) in the hollow of his hand, quenched his thirst; as for those who drank freely from it, their thirst was not quenched."
Ibn Jarir reported that Al-Bara' bin `Azib said, "We used to say that the Companions of Muhammad who accompanied him on the battle of Badr were more than three hundred and ten, just as many as the soldiers who crossed the river with Talut. Only those who believed crossed the river with him." Al-Bukhari also reported this.
This is why Allah said:
فَلَمَّا جَاوَزَهُ هُوَ وَالَّذِينَ ءَامَنُواْ مَعَهُ قَالُواْ لاَ طَاقَةَ لَنَا الْيَوْمَ بِجَالُوتَ وَجُنودِهِ
(So when he had crossed it (the river), he and those who believed with him, they said: "We have no power this day against Jalut (Goliath) and his hosts.")
This Ayah indicates that the Israelites (who remained with Saul) thought that they were few in the face of their enemy who were many then. So, their knowledgeable scholars strengthened their resolve by stating that Allah's promise is true and that triumph comes from Allah Alone, not from the large numbers or the adequacy of the supplies. They said to them:
كَم مِّن فِئَةٍ قَلِيلَةٍ غَلَبَتْ فِئَةٍ كَثِيرَةً بِإِذْنِ اللَّهِ وَاللَّهُ مَعَ الصَّـبِرِينَ
("How often has a small group overcome a mighty host by Allah's leave" And Allah is with As-Sabirin (the patient).)

When they were given the Ark back, they accepted him as their king and went out with him to fight. (And when Saul set out) went forth (with the army) through a wasteland and became very thirsty, they asked him to provide them with water, (he) i.e. Saul (said: Lo! Allah will try you by a river) Allah will test you by a flowing river. (Whosoever therefore drinketh thereof) from the river (he is not of me) he is not going to be with me in the fight against my enemy and will not go further, (and whoever tasteth it not he is of me) against my enemy, but then he made an exception, (save him who taketh (thereof) in the hollow of his hand) and this was enough for them, their beasts and transportation. (But they drank thereof) when they reached the river however they drank as much as they wanted to, (all save a few of them) 313 men who did not drink except as they had been directed. (And after he had crossed) the river, (he) i.e. Saul (and those who believed with him, they said) to each other: (We have no power this day against Goliath and his hosts. But those who knew) and were convinced (that they would meet Allah) in person after they died (exclaimed: How many a little company) of believers (hath overcome a mighty host) of unbelievers (by Allah's leave!) by the help of Allah. (And Allah is with the steadfast) He assists the steadfast in war by giving them victory.

EN

And when Saul went forth with the hosts from the Holy House sc. Jerusalem the heat was intense and so they asked him for water; he said ‘God will try test you in order to distinguish the obedient among you from the disobedient with a river between Jordan and Palestine whoever drinks of it of its water is not of me is not of my followers and whoever tastes it not he is of me except for him who scoops up with his hand’ ghurfa or gharfa ‘a scoop’ satisfying himself therewith and not taking more he is also of my followers. But they drank of it when they reached it and saw that it was abundant except a few of them who restricted themselves to a scoop it is reported that one scoop was enough for each man and his horse and they numbered over three hundred; and when he crossed it with those who believed the ones who confined themselves to the one scoop they the ones that drank profusely said ‘We have no power today against Goliath and his troops’ that is no power to fight them and they were cowardly and did not cross it. Those who thought with certainty that they would meet God at the Resurrection and these were the ones that crossed it said ‘How often kam ‘how’ functions as a predicate meaning kathīr ‘many’ a little company group of men has overcome a numerous one by God’s leave by His will; and God is with the patient’ providing them with help and assistance.

EN

Verse 249: قَالَ إِنَّ اللَّـهَ مُبْتَلِيكُم بِنَهَرٍ (He said: Allah is going to test you by a
river).
The wisdom behind this test, as perceived by this humble commentator, appears to be as follows. Not difficult to imagine is the excitement created on such occasions but there are not many who would stay firm in their hour of trial. And should such a time come, the weakness shown by such people becomes contagious making others panic as well. Allah Almighty willed that such people be pruned out. This purpose was accomplished by this test, which is very appropriate, because steadfastness is necessary in fighting. So, being patient, when water is made available without asking in a state of intense thirst, is a proof of steadfastness, and dashing for water is a proof of its absence. Later on comes the unusual: Those who drank too much water became mysteriously more incapacitated. This has appeared in Ruh al-Ma'ani on the authority of Ibn Abi Haim from Ibn ` Abbas ؓ . Now the events and sayings mentioned in this story tell us that there were three kinds of people among them:
(1) The weak in faith who failed to make the grade in their hour of
trial.
(2) The perfect who fully succeeded in their trial but did feel concerned about how low they were in numbers.
(3) The most perfect who did not bother even about that.

EN

About three hundred years after Moses and about one thousand years before Christ the Philistines attacked the Israelites and annexed most of the region of Palestine. After a period of time the Israelites wished to take some action against the Philistines, so that they might recover their lands from them. At that time there was a prophet called Samuel among them. Living in an ancient city in Syria, known as Rama, Samuel was in charge of the community matters of the Israelites. Therefore, a delegation met him and said to him, ‘Now that you have aged, you should appoint a king from amongst us, in order that we may wage war against our enemies under the command of our leader.’ Although Samuel did not have a good opinion of the character of the Israelites, he agreed to their request and promised to appoint a King for them. Therefore, he appointed a brave youth, Saul, who belonged to the tribe of Benjamin. Saul (Talut) set forth with the army to meet the enemy. On the way they had to cross the river Jordan. Since Saul was aware of the weaknesses of the Israelites, he employed a simple method to test them. He gave the order that, while crossing the river, no one was to drink more than a handful of water from it. The majority of the Israelites failed the test. However, God was with them and they emerged victorious under the leadership of Saul. A decisive role was played in this battle by David, a young Israelite soldier who was one of those who had full confidence in God. The feat he performed was to kill the enemy’s supreme commander, Goliath (Jalut). Upon the fall of Goliath, the Philistine army broke ranks and fled.