Assalaamu alaykum. I have a question regarding glue and Ghusl (ritual shower). I went to the hospital due to my heart condition, and they left a machine on my body for 3 days. It has left glue on my body that is not coming off unless I rub it hard, to the point that the skin starts bleeding. I would like to know whether my Ghusl is valid, because it is on both my rib cages and near the heart. Thank you in advance.

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

If it is not possible to remove that glue except with hardship, as mentioned, then it is sufficient for you to remove what does not harm you by removing it, since Allah does not burden a soul with more than it can bear, and whatever remains after that does not affect the validity of Ghusl, especially if it is an insignificant amount. Many scholars of Fiqh are not strict with regards to an insignificant barrier (between water and skin).

Kash-shaaf Al-Qinaa' reads:

"A little dirt under a fingernail does not affect purification (Ghusl or ablution), even if it prevents the water from reaching the skin, as this is quite common, because if ablution was not valid with it [dirt], then the Prophet would have clarified it since it is not permissible to delay a clarification after the time of need for it. Shaykh Ibn Taymiyyah also considered that any insignificant substance on the body, regardless of which part of the body it is on, that prevents water from reaching the skin, like blood, dough or the like, takes the same ruling. This is the view chosen by him (Ibn Taymiyyah) based on analogy with the little dirt under the fingernail."

Even if the remnants of the glue is much, it still does not affect the validity of purification.

Al-Hattaab Al-Maaliki quoted the comparison for whoever performs ablution while he has ink on his hands in Mawaahib Al-Jaleel from Maalik, and he saw it after he had prayed in this condition:

"'This does not harm him if he had passed the water on the ink ... if he was the one who was writing (i.e. who used the ink in writing).' It is as if he is of the view that the writer cannot avoid ink stains contrary to someone other than a writer. His statement, 'if he had passed the water on the ink', is clear in giving the same ruling to the ink as to what is under it. If someone said: ink is not a barrier; rather, it takes the same ruling as substances that dye, like henna; we answer by saying: it is not the same thing; henna is removed while its effect remains, contrary to ink. If ink does not prevent water from reaching the skin, then it would not have any meaning to say that it must be the one who was writing (who is excused if his skin is stained with ink)."

Ar-Ramli, from the Shaafi'i School, was asked about a type of tattoo on the body that is called "daqq", does it prevent the water from reaching the skin so that the person must remove it whether or not he had put it by transgression [purposefully while he knows tattoos are forbidden], and is it impure according to the apparent ruling even if it is placed in a runny substance or a little water, does it render it impure?

He replied:

"If he had put the tattoo on his body willingly while he was an adult (accountable for his actions), and he does not fear harm from removing it that would make it permissible for him to perform Tayammum (dry ablution), then its existence prevents the purification of the spot it is on; otherwise (if he fears harm from removing it), he is excused if it remains. This applies to him and to others (who come in contact with that spot), and his purification is valid. In the case where he is not excused and this spot comes in contact with a little water or a runny or moist substance, it renders it impure."

So, if the purification of someone who has a tattoo is valid if he fears harm from removing it although he did it by transgression [because tattoos are forbidden] and although it renders the post it is on impure, then the purification of the person who has remnants of the substance mentioned in the question (glue) while it cannot be removed except with great hardship or harm is valid with greater reason.

For more benefit, please refer to fatwas 278056 and 252436.

Allah knows best.