[Of] all belonging [to those with] dangerous [and] great sicknesses, [they are] mostly due [to] past lives’ [and the] present life’s [negative] karma [from] killing then attained.
And [these] people with sicknesses, must sever [from] sexual matters, [at least for the time being]. Then can [there be] swift healing, [if lifespan is not at its end].
Desiring [to] eradicate past [and] present [negative] karma [from] killing, [there] must [be] abstaining [from] killing, [and with] eating [as] veg[etari]an.
Also, [with] utmost sincere mindfulness [of Amitā(bha)] Buddha[‘s name: Āmítuófó], and[/or] mindfulness [of] Guān[shì]yīn [Bodhisattva’s name], thus definitely [will they] able [to have] swift healing, further able [to] cultivate virtues and plant good roots.
If resenting karmic sicknesses, [and] eradicating these healing methods [above, it will be] definitely difficult [to have] full healing.
These people, and their families’ Fathers, Mothers, wives [and] children, hoping [for] healing [with] minds anxious, not necessarily [will] not [be] willing [to] rely [on this advice to] follow [accordingly, to create and dedicate meritorious virtues to the concerned].
If willing [to] rely [on this to] follow, thus then planting good roots [for] transcending [the] world.
From now giving rise [to the] right mind [of] faith, [to] later perhaps due [to] this, liberating [from the cycle of] birth [and] death, transcending [the] ordinary [to] enter [the] sagely. Thus, for them [and] for you, all [will] have great benefits.
Pure Land Tradition’s 13th Patriarch Great Master Yìnguāng
(Letter to Doctor Mǎ Xīngqiáo)
 Of course, proper medical advice should also be responsibly and reasonably (but not overly) sought for care when sick, to expedite healing, unless confirmed to be unnecessary or too late.
 For practice, mindfulness of Āmítuófó’s name will do for healing, as he already is the ‘Unsurpassable King Of Healers’ (无上大医王), although those who habitually associate Guānshìyīn Bodhisattva more with healing can practise with her name too.
 See too, the first Related Article below, on the need to shift priorities to aspire only for reaching Pure Land if severely sick, to the point of possibly already dying.
 See too, the second Related Article on when it is best to only practise mindfulness of Āmítuófó’s name, with the straight[forward] mind.
Namo Amituofo : Translation and notes by Shen Shi’an
What Attitude To Have When Severely Sick?
Why Be Mindful Of Buddha When Severely Sick Without Praying For Longevity?