Is the Islam valid for one who utters the Two Testimonies with the intention of entering Islam—if blaspheming God is disbelief (kufr)—and with the intention of reward—if it is a sin—after a sheikh told him that he must believe in the disbelief (kufr) of blasphemy in order for his Islam to be valid?

Reviling Almighty Allah is, by scholarly consensus, an act of disbelief (kufr) and apostasy (riddah) from Islam. If one repents, expresses remorse, and recites the Two Testimonies of Faith (Shahadatain), their Islam is valid, even if they doubt whether disbelief truly occurred, because repentance obliterates what came before it. Imam Bukhari narrated that polytheism (shirk) is more subtle than the creeping of an ant, and that the Prophet, peace and blessings be upon him, taught us to say: "O Allah, I seek refuge in You from associating partners with You knowingly, and I seek Your forgiveness for what I do not know." Repentance from sin is obligatory, and if it is general, all sins are forgiven. If a person's apostasy is established, their testimony that there is no god but Allah and that Muhammad is the Messenger of Allah is sufficient for their return to Islam, without needing to question them about what they were accused of. Whoever wishes to dispel doubt with certainty should renew their repentance and recite the Two Testimonies of Faith.