Two types of plural
In several languages, there are two types of plurals, one is a plural of numbers to refer to something that occurs in a quantity of more than one. The other plural is a plural of respect.
a. In the English language, the Queen of England refers to herself as ‘We’ instead of ‘I’. This is known as the ‘royal plural’.
b. Rajiv Gandhi, the ex-Prime Minister of India used to say in Hindi "Hum dekhna chahte hain". "We want to see." ‘Hum’ means ‘We’ which is again a royal plural in Hindi.
c. Similarly in Arabic, when Allah refers to Himself in the Qur’an, He often uses Arabic word 'Nahnu' meaning ‘We’. It does not indicate plural of number but plural of respect.
Tawheed or monotheism is one of the pillars of Islam. The existence and uniqueness of one and only one God is mentioned several times in the Qur’an. For instance in Surah Ikhlas, it says :
"Say He is Allah the One and Only."
[Al-Qur’an 112: 1]
If Allah has sealed the hearts of the Kuffar i.e. non-Muslims, then why are they to be blamed for not accepting Islam?
1. Allah has sealed the hearts of those who are continuously bent on rejecting the truth
Allah (swt) mentions in Surah Al Baqarah chapter 2 verses 6 and 7
"As to those who reject Faith, it is the same to them Whether thou warn them or do not warn them; they will not believe.
Allah hath set a seal on their hearts and on their hearing, and on their eyes is a veil; great is the penalty they (incur)."
These verses do not refer to common Kuffar who reject faith. The Arabic words used are al-lazina kafaroo, those who are bent on rejecting the truth. It will not make any difference to such people whether you warn them or not, they will not believe. Allah has set a seal on their hearts and on their hearing and on their eyes is a veil. It is not because Allah has set a seal on their hearts that these kuffar do not understand and believe, but it is the vice-versa. It is because these kuffar are bent on rejecting the truth and whether you warn them or not they will not believe, that Allah has set a seal on their hearts. Therefore Allah is not to blame, but these kuffaar who are bent on rejecting the faith are responsible.
2. Example of teacher predicting a student will fail
Suppose an experienced teacher, before the final examinations, predicts that a particular student will fail in the exams, since the student is very mischievous, not attentive in class and does not do his homework. If after the student appears for the examination, he fails, who is to be blamed for the student failing: the teacher or the student? Just because the teacher predicted, it does not mean that the teacher is to be blamed but the student himself is responsible for his failure.
Similarly Allah (swt) knows in advance that there are some people who are bent on rejecting the faith and Allah has put a seal on their hearts. Thus these non-Muslims themselves are responsible for rejecting the faith and not Allah (swt).