Praise be to Allah, and peace and blessings be upon the Messenger of Allah. To proceed:
The hadiths that promise Paradise to those who say “There is no god but Allah” do not refer to merely uttering these words with the tongue. Rather, they refer to saying them while believing in their meaning and accepting what they imply: worshipping Allah alone and affirming His absolute Oneness.
The Prophet ﷺ said:
“No servant says, ‘There is no god but Allah,’ and then dies upon that except that he will enter Paradise.”
Agreed upon.
Whoever dies upon monotheism and faith, without committing anything that nullifies the foundation of Islam, will ultimately enter Paradise, even if they have sins and acts of disobedience.
Allah Almighty says:
“Indeed, Allah does not forgive associating others with Him, but He forgives anything less than that for whom He wills.”
[Qur’an 4:48]
Therefore, a Muslim who dies upon monotheism while having committed major sins other than shirk is under Allah’s will: if Allah wills, He may forgive them, and if He wills, He may punish them for some of their sins. However, they will not remain eternally in Hell as a disbeliever does.
As for someone who pronounces the testimony of faith with their tongue while their heart rejects it, such as a hypocrite whose hypocrisy is in belief, merely pronouncing it will not benefit them because true faith is absent from their heart.
Allah described the hypocrites as declaring the testimony with their tongues:
“When the hypocrites come to you, they say, ‘We bear witness that you are certainly the Messenger of Allah.’”
Then He says:
“And Allah bears witness that the hypocrites are certainly liars.”
[Qur’an 63:1]
Likewise, whoever says “There is no god but Allah” and then commits something that contradicts its meaning, such as major shirk, will not benefit from merely uttering it while violating the foundation of monotheism.
In conclusion: The virtue of “There is no god but Allah” mentioned in the hadiths applies to the one who says it while believing in its meaning and dies upon monotheism. It does not mean merely moving the tongue with these words. A sinful monotheist will ultimately enter Paradise, even if punished beforehand. But whoever dies upon shirk, disbelief, or hypocrisy in belief will not benefit from words spoken by the tongue without fulfilling their true meaning.
And Allah knows best.