لَعَلّ is an article and is one of the sisters of إِنَّ , the meaning is – may be, i.e that is it gives a sense of chance and not surety, it doesnot guarantee anything. For example see the following verse of the Qur’an:-
وَلَنُذِيقَنَّهُمْ مِنَ الْعَذَابِ الْأَدْنَى دُونَ الْعَذَابِ الْأَكْبَرِ لَعَلَّهُمْ يَرْجِعُونَ
Meaning of the above cited verse
And indeed We will make them taste of the lighter chastisement before the greater chastisement , may be that they return.
If you take the meaning of لَعَلّ to be guaranting return then will the verse give any meaning?
Actually, the lighter punishment is given to realize that how the punishments are painful may be by understanding that they might change their minds. In the similar sense the word لَعَلّ is used in the verse 2:183.
Food and water are the basic requirements of a human being and therefore is one of the weaknesses. The very thought of living without food and water frightens mankind so much that he gets ready to do anything so as to not face that situation. And if any time in his life he comes across such a situation he has all the chances of loosing his intellect due to the pain of hunger and thirst and added to it is the fear of death. In such a situation it is highly possible that he may submit to the whisper of the Satan and break the limitations prescribed by Allah. For example he may commit suicide instead of being patient, he may be incited with enemity, hatred, killing for the struggle for existence.
This kind of situation might come during :–1. War.
2. Foreign invasion
6. Earth quakes and other Natual calamities,
7.when one is a captive
8.one never knows
Long and lengthy hours of staying without food and water may create a confidence that we can survive without food and water for long periods and such a confidence gives the spirit to fight back the situation in the best possible way but in no way takes a guarantee that man will not submit to Satan. Above all is the free will and its use, it only gives a training to not only become capable of staying without food and water but also it gives a sense of confidence and intellect to remain within the limits set by Allah in all circumstances.
Muttaqi as a whole refers to one who lives life in every circumstance within the limitations set by Allah for mankind. It includes doing of all actions that Allah has prescribed for us and it also includes forsaking of all the actions that Allah has prohibited for us.
Even after the realization that one can stay without food and water for a preety long period , anyone can pass the limitations set by Allah with regards to peace and love and may commit ignorance and oppression and become enemies of mankind for the satisfaction of selfishneeds.