When ignorance of Tawhid becomes one of the barriers to takfir, the scales become distorted. Whereas ignorance of Tawhid is a barrier to Islam, because knowledge of the meaning of the testimony is a condition among the conditions for its realization.
Allah ta’ala says:
{Except those who testify to the truth while they know.} (Surah al-Zukhruf 43/86)
“Except those who testify to the truth” — meaning: “There is no deity except Allah.”
“while they know” — meaning: they know in their hearts the meaning of what they have uttered with their tongues.
Ibn Jarir al-Tabari (310 AH) said:
“Except those who testify to the truth” — their testimony to the truth is their acknowledgment of the Tawhid of Allah. Meaning by that: except those who believe in Allah, while they know the reality of His Tawhid.
“Except those who testify to the truth while they know” — they are those who bear the testimony of truth, thereby singling Allah out, and sincerely affirming His Oneness, with knowledge and certainty of that.”
Ibn Jarir al-Tabari (310 AH), when interpreting the statement of Allah ta’ala, “That is because they are a people who do not know”, said:
Ibn Humayd narrated to us; he said: Ya‘qub narrated to us, from Ja‘far, from Sa‘id, who said:
The Messenger of Allah ﷺ went out on a military expedition and encountered the enemy. The Muslims brought out a man from among the polytheists and thrust their spearheads toward him. The man said:
“Remove your weapons from me, and let me hear the Word of Allah!”
They said:
“Testify that there is no deity except Allah and that Muhammad is His servant and His Messenger, renounce the equals, and disassociate yourself from al-Lat and al-‘Uzza!”
He said:
“Then I call you as witnesses that I have done so.”
So this was a man who bore the testimony of truth — “There is no deity except Allah” — knowing its meaning, which consisted of renouncing the equals and disassociating himself from the false deities.
Thus, the testimony is not called a testimony except with knowledge of that which one has testified to. And this is among the clearest proofs that knowledge is a condition among the conditions of the testimony.
Allah ta’ala says:
{So know that there is no deity except Allah.} (Muhammad 47/19)
Ibn Jarir al-Tabari (310 AH) said:
Allah ta’ala says, addressing His Prophet Muhammad ﷺ:
“So know”, O Muhammad, that there is no deity worthy of worship, nor is divinity appropriate or suitable for anyone, and whom it is permissible for you and creation to worship, except Allah, who is the Creator of creation and the Owner of everything, and everything besides Him acknowledges His Lordship.
The Messenger of Allah ﷺ said:
“Whoever dies while knowing that there is no deity except Allah will enter Paradise.” (Sahih Muslim, Hadith no. 26, Kitāb al-Īmān )