I have a friend whose health is not so good. In a way he is the healthiest, never sick in bed. But he is skinny. Correct me if I'm wrong or ignorant in this matter I heard there are verses or chapters in the Quran that help to (give Shifa'a) heal a person. Do you think they might help him to gain some health (in the sense some good weight). Or are there some Du'aa that can help. Yours replies are most valuable.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Undoubtedly, the Quran is a cure as Allaah Says (what means): {Say, ‘It is, for those who believe, a guidance and cure.”} [Quran 41:44]. Allaah also Says (what means):  {And We send down of the Quran, that which is healing and mercy for the believers…} [Quran 17:82]

The scholars have two opinions concerning the meaning of "cure" in the verse.

The first opinion: it is a cure for the diseases of the heart, such as doubt in faith, hypocrisy, polytheism, resentment, and removing the cover from one's heart that prevents one to perceive the signs that show the way towards Allaah.

The second opinion: it is a cure for the apparent (physical) diseases; it is achieved by performing Ruqyah, seeking refuge in Allaah, and the like.

As-Shawkaani said: "There is nothing which prevents from understanding the cure for both meanings." This is the correct opinion.

Therefore, if you recite some verses of the Quran on your friend, we hope that it will benefit him in general and for his thinness.

However, we stress that you should consult doctors and specialists in the field, as a way of taking all means available. The Prophet said: "Allaah has not sent down a disease except that he sent down a cure for it; but some people might know it and some might not." [Ahmad]

It should be mentioned that despite the Ruqyah with the Quran or the Sunnah is a means of cure, sometimes it does not benefit the person upon whom the Ruqyah is performed if he does not fully rely on Allaah or does not believe in the effectiveness of the recitation, or he is engaged in forbidden matters that prevent his supplications from being answered, such as consuming ill-gotten money, like Riba (interest and usury) and the like, or that the place where the Quran is recited on the patient contains forbidden objects that bring devils and prevent angels from entering it, like statues, hanged pictures, the presence of dogs and the like.

Therefore, for the Ruqyah to be beneficial, there should be nothing that prevents its effectiveness and the person should meet the conditions such as relying on Allaah, having faith in Him and in His Book.

Finally, we do not know of a special verse or chapter or Prophetic supplications that can particularly help in gaining weight.

Allaah Knows best.