Muhammad Rida Al-Muzaffar writes:

فمن لم يكن مجتهدا ولا محتاطا ثم لم يقلد المجتهد الجامع للشرائط فجميع عباداته باطلة لا تقبل منه وإن صلى وصام وتعبد طول عمره إلا إذا وافق عمله رأي من يقلده بعد ذلك وقد إتفق له أن عمله جاء بقصد القربة إلى الله تعالى

“Now if a person was neither a jurist nor used caution (Ihtiyat), whereupon he did not imitate a qualified jurist (Taqlid), all his worship is invalid and will not be accepted by him, even if he prayed, fasted and performed worship all his life, unless his action is in accordance with the opinion of the one he imitated (Taqlid) and he succeeded in performing his action with the intention of getting closer to God.” [Aqa’id-ul-Imamiyyah, page 19]

Comment:

It is not the jurists, without whose obedience the worship will not be accepted, but the fourteen infallible leaders of this nation [Read here!]