Quotation for Ketubot 207:13

This question obviously refers to a terminally ill patient who can live for only several weeks or months, at most. Such patients often should not be treated. The key concern is their quality of life. In cases of intractable pain, we have clear instructions from the account of the death of Rebbe, the compiler of the Mishnah, in Talmud Kesubos 104[a]. The Talmud describes how his students prayed that he would remain alive. His maidservant, seeing the great suffering he was enduring, prayed that the angels above would meet with success [in their prayers for Rebbe's soul to return to Heaven, [so that the rabbis' prayers for his continued life] would not be accepted.