Answered by Ustadh Salman Younas
Question: Once I was leading my father in prayer and I accidentally said something in English. I have since repeated the prayer but when I asked him about it he jokingly told me not to worry as Allah does not speak English. Is my father Muslim after this joke?
Answer: assalamu `alakum
Your father is certainly a Muslim. Alhamdulilah. His statement is not one that renders him a disbeliever, nor one that is disbelief.
Islam is not something that individuals can be “removed” from so casually. When someone enters Islam, that person becomes inviolable; his/her person, his/her honor, his/her wealth etc.. This inviolability is magnanimous in the eyes of God, His Prophet (God bless him), and the early Muslims. Indeed, as the Prophet, Ibn Umar and others gazed upon the Ka’aba they would state, “the inviolability of a believer is greater with God than your inviolability.” [Sunan al-Tirmidhi; Sunan Ibn Majah]
Those who are quick to engage in throwing people outside the fold do not understand this inviolability. Given the various prophetic traditions in explicit condemnation of anathema (takfir), such as, “accusing a believer of disbelief is akin to killing him,” it is often surprising to see how individuals can entertain it so easily
This manner of thinking is not only contrary to the religion of Islam because it fails to recognize the rank of the believer, but it it also involves ill-opinion, false testimony, suspicion, causing division, and much more that the religion warns against. This is why we must always be cautious and circumspect when it comes to such judgments, which, for the most part, do not concern us as laymen.
For some more details on this issue, please refer too:
What Takes a Person Out of the Fold of Islam?
Please also not that the reproachful nature of the answer is not meant to be directed at you as an individual but simply to get across the seriousness of engaging in takfir.
Checked & Approved by Shaykh Faraz Rabbani