What should I do about my will if I have been diagnosed with a serious illness?

Agreed. It is measured as a bequest, not as a gift. The Kuwaiti Mawsu’a states the agreement in one sentence naming every school: “where the sick man has heirs, the jurists of the Hanafis, the Shafi’is, the Malikis and the Hanbalis have agreed that the sick man’s gift takes effect in this case if a third of his property will carry it” — and “if it exceeds the third, the excess depends on the heirs’ ratification: if they allow it, it goes through; if they reject it, it is void.” The authority the schools give for treating a death-illness transfer this way is Sa‘d ibn Abi Waqqas’s hadith — the same text that fixes the one-third cap on a will — and al-Tahawi’s comment on it is the whole doctrine in a line: the Prophet “made his charity during his illness come out of the third, just as his bequests come out of the third after his death”. Where the recipient is one of the heirs, the Mawsu’a again names the Hanafis, the Shafi’is on their preferred view, the Malikis and the Hanbalis: the gift depends on the remaining heirs’ consent whether it is less than a third or more — expressly “as in a bequest to an heir”. The practical upshot for a Canadian family is that a transfer signed in a hospital bed is not taken out of the faraid reckoning by the fact that it was signed before the death. It is brought back in and measured against the third. We checked this point; the schools do not differ on it.

Shared evidence: al-Mawsu’a al-Fiqhiyya al-Kuwaytiyya, “Marad al-Mawt” sec. 5 — “the jurists of the Hanafis, the Shafi’is, the Malikis and the Hanbalis have agreed that the sick man’s gift takes effect... if a third of his property will carry it” · The same entry, on the excess and on the gift to an heir — the surplus “depends on the heirs’ ratification”, and a gift to an heir depends on the others’ consent “whether it is less than a third or more — as in a bequest to an heir” · Sa‘d ibn Abi Waqqas’s hadith, quoted by the Mawsu’a as the proof, with al-Tahawi’s comment that the Prophet “made his charity during his illness come out of the third, just as his bequests come out of the third after his death” · Sahih al-Bukhari 2742 — the underlying hadith · Sahih Muslim 1628a — the underlying hadith.

Not covered by this finding: two cases the agreement above does not reach. First, the donor who leaves no heirs at all: there the Hanafis let the gift take effect in full even if it swallows everything, while the Shafi’is and Malikis still void it above the third, on the reasoning that the property would otherwise go to the Muslims at large and there is nobody to ratify on their behalf. Second, a non-preferred view of al-Shafi’i that a death-illness gift to an heir is not merely suspended on the other heirs’ consent but void outright. Separately, where the donor dies owing debts that swallow the estate, the analysis is not about the third at all: the gift does not take effect against the creditors, and the Mawsu’a records that they may set it aside and bring the property back into the distribution among them. — not yet researched school by school. Treat that as open and ask a scholar of your school.