Under the commentary of the verse, “Allāh does not forgive anything being associated with Him but He forgives whoever He wills for anything other than that” (4:116), Shāh Ismā‘īl Shahīd explains that all sins apart from shirk are pardonable but the crime of shirk is unpardonable. Then he says:
Further, if it is shirk of the highest order from which a person becomes a disbeliever, his punishment* will be an eternity in hell – he will never come out of it, nor will he experience any comfort in it. The shirk that is of a lesser order, the punishment that is determined for it with Allāh will be received.** The remaining sins, the punishments that are determined for them with Allāh are dependent on Allāh’s choice: if He wills He will mete it out and if He wills He will pardon. (Taqwiyat al-Īmān, p. 19)
Thus in Taqwiyat al-Imān itself, Shāh Ismā‘īl recognises that some shirk will take a person out of Islām and some shirk will not. It is in this backdrop that his general statements on this subject need to be understood.
* Here the discussion is over a person who commits these crimes (major shirk, minor shirk, or all other sins) and dies without having repented from them. If a person sincerely repents from them before death, he will not be taken to task for them.
** It should be noted that there is disagreement on this question, over whether lesser shirk will be treated like greater shirk and thus remain unpardonable (but unlike greater shirk not necessitate an eternity in hell) or will be treated like all other sins (major or minor) and thus be subject to Allāh’s will.