Allah (swt) dried it up and responded to the letter to prove to the people that it is He who controls it.
i read about something like this to happen in future times in the previous scriptures and in the hadith when the yajuj majuj surround the camp of believers:
A day of darkness and of gloominess, a day of clouds and of thick darkness, as the morning spread upon the mountains:
a great people and a strong; there hath not been ever the like, neither shall be any more after it, even
to the years of many generations.
A fire devoureth before them; and behind them a flame burneth:
the land is as the garden of Eden before them, and behind them a desolate wilderness; yea, and nothing shall escape them.
The appearance of them is
as the appearance of horses; and as horsemen, so shall they run.
Like the noise of chariots on the tops of mountains shall they leap, like the noise of a flame of fire that devoureth the stubble, as a strong people set in battle array.
Before their face the people shall be much pained: all faces shall gather blackness.
They shall run like mighty men; they shall climb the wall like men of war; and they shall march every one on his ways, and they shall not break their ranks:
Neither shall one thrust another; they shall walk every one in his path: and when
they fall upon the sword, they shall not be wounded.
They shall run to and fro in the city; they shall run upon the wall, they shall climb up upon the houses; they shall enter in at the windows like a thief......
.....Let the priests, the ministers of the LORD, weep between the porch and the altar, and let them say,
Spare thy people, O LORD, and give not thine heritage to reproach,
that the heathen should rule over them:
wherefore should they say among the people, Where is their God?
18Then will the LORD be jealous for his land, and pity his people.
Yea, the LORD will answer and say unto his people, Behold, I will send you corn, and wine, and oil, and ye shall be satisfied therewith: and I will no more make you a reproach among the heathen:
But I will remove far off from you the northern army
, and will drive him into a land barren and desolate, with his face toward the east sea, and his hinder part toward the utmost sea, and his stink shall come up, and his ill savour shall come up
, because he hath done great things.
Fear not, O land; be glad and rejoice: for the LORD will do great things.
Be not afraid, ye beasts of the field: for the pastures of the wilderness do spring, for the tree beareth her fruit, the fig tree and the vine do yield their strength.
Be glad then, ye children of Zion, and rejoice in the LORD your God: for he hath given you the former rain moderately, and he will cause to come down for you the rain, the former rain, and the latter rain in the first month.
And the floors shall be full of wheat, and the fats shall overflow with wine and oil.
And I will restore to you the years that the locust hath eaten, the cankerworm, and the caterpiller, and the palmerworm, my great army which I sent among you.
And ye shall eat in plenty, and be satisfied, and praise the name of the LORD your God, that hath dealt wondrously with you: and my people shall never be ashamed.
And ye shall know that I am
in the midst of Israel, and that
the LORD your God, and none else: and my people shall never be ashamed.
It will be under such conditions that Allah will reveal to Jesus the following words:
'I have brought forth from among My servants such people against whom none will be able to fight;
you take these people safely to Tur
Then, Allah will send Gog and Magog
and they will swarm down from every slope.
The first of them (Gog and Magog) will pass the lake of Tiberias (Sea of Galilee) and drink out of it.
And when the last of them passes, he will say: 'There was once water there.'
Jesus and his companions will then be besieged here (at Tur mountain, and they will be so hard pressed)
to the extent that an ox will be more valuable to them than one hundred Dinars (gold coins).
Allah's Messenger صلى الله عليه وسلم said, Jesus, and his companions will supplicate to Allah,
Who will send to them (Gog and Magog)
insects (which will attack their necks) and in the morning, they would perish as one single person.
Allah's Messenger صلى الله عليه وسلم said, Jesus, and his companions will then come down (from Tur mountain)
and they will not find as much space as a single span that is not filled with decomposed remains and stench of Gog and Magog's corpses
Allah's Messenger صلى الله عليه وسلم said, Jesus, and his companions will then supplicate to Allah
who will send birds whose necks would be like those (the necks) of Bactrian camels
and they will carry them (Gog and Magog)
away and throw them where Allah wills.
Then Allah will send rain which no house of mud-bricks or (tent of) camel-hair will keep out and it will wash the Earth until it resembles a mirror.
Then, the Earth will be ordered (by Allah) to bring forth its fruit and restore its blessing and,
as a result thereof, pomegranate will grow that will be enough for a group of people to eat and seek shelter under its skin.
A dairy cow will give so much milk that (will be enough for) a group of people to drink.
The milking camel will give so such milk that a whole tribe will be able to drink from it...