Shaykh 'Abdul-'Aziz bin Baz, rahimahullah, was asked, 'Who are the ones who will be excused for ignorance about 'aqidah and matters of fiqh?' to which he replied as follows.
Praise be to Allah.
Claiming that one is ignorant or using this as an excuse is a matter which needs further discussion. Not everyone can be excused for his ignorance. With regard to the things which were brought by Islam, which the Messenger, peace and blessings of Allah be upon him, explained and which were made clear in the Book of Allah and are widely known among the Muslims, no claim of ignorance will be accepted in these cases, especially in matters with have to do with 'aqidah and the basics of religion.
Allah sent His Prophet, peace and blessings of Allah be upon him, to teach the people their religion and explain it to them, and he conveyed the message clearly and explained to the ummah the truths of their religion. He explained everything and left them with a clear path which is always obvious. In the Book of Allah there is guidance and light. If some people claim to be ignorant about things which are known to be essential parts of the religion and which are well known among the Muslims, such as claiming to be ignorant about shirk and worshipping anything other than Allah, or claiming that salah is not obligatory, or that fasting Ramadan is not obligatory, or that paying zakah is not obligatory, or that doing hajj when one is able to is not obligatory - in these and similar matters, claims of ignorance are unacceptable from those who live among the Muslims, because they are matters which are well known among the Muslims. They are known to be essential parts of the Muslim religion and are widely known among the Muslims, so the claim of ignorance of these matters is unacceptable.
This is the case if a person were to claim that he does not know that what the mushrikeen do at the graves or idols is wrong, when they call upon the dead, seek their help, offer sacrifices to them and make vows to them, or offer sacrifices to the idols, stars, trees or rocks; or seek healing or help against their enemies from the dead or idols or jinn or angels or Prophets. All of these are things which are known essentially in the religion that they are major shirk (al-shirk al-akbar).
Allah explained this clearly in His Book, and His Messenger, peace and blessings of Allah be upon him, explained it clearly. He remained in Makkah for thirteen years warning the people against this shirk and he preached the same message in Madinah for ten years, explaining to them that it is obligatory for their worship to be purely and sincerely for Allah Alone and reciting to them the Book of Allah such as the verses (interpretation of the meaning):
"And your Lord has decreed that you worship none but Him."
"You (Alone) we worship, and You (Alone) we ask for help (for each and everything)."
"And they were commanded not, but that they should worship Allah, and worship none but Him Alone (abstaining from ascribing partners to Him)."
"So worship Allah (Alone) by doing religious deeds sincerely for Allah's Sake only. Surely, the religion (i.e. the worship and the obedience) is for Allah only."
"Say (O Muhammad): 'Verily, my salah (prayer), my sacrifice, my living, and my dying are for Allah, the Lord of the 'Alamin (mankind, jinn and all that exists). He has no partner. And of this I have been commanded, and I am the first of the Muslims.' "
And Allah says, addressing His Messenger, peace and blessings of Allah be upon him (interpretation of the meaning):
"Verily, We have granted you (O Muhammad) Al-Kawthar (a river in Paradise). Therefore turn in prayer to your Lord and sacrifice (to Him only)."
"And the mosques are for Allah (Alone), so invoke not anyone along with Allah."
"And whoever invokes (or worships), besides Allah, any other ilah (god), of whom he has no proof; then his reckoning is only with his Lord. Surely, al-kafirun (the disbelievers in Allah and in the Oneness of Allah, polytheists, pagans, idolaters) will not be successful."