Question: How much effective is the enunciation of Shahaadah (testimony of faith)? May Allaah grant you success!
Answer: First of all, it is necessary for a person to declare the Shahaadah in order to be called a Muslim. A person will remain a Kaafir (disbeliever) until they declare the Shahaadah. However, the Shahaadah alone is not enough, as it is necessary to believe sincerely that the phrase ‘there is no god but Allaah’ means that no one ever has the right to be worshipped except Allaah (Exalted be He). If a person pronounces this phrase and yet associates other deities along with Allaah in worship, they will be behaving like hypocrites whose practice is no more than lip service. In such a case, their declaration of Shahaadah will avail them naught. Allaah (Glorified be He) states, Verily, the hypocrites will be in the lowest depth (grade) of the Fire; no helper will you find for them. Allaah (Exalted be He) also says, And of mankind, there are some (hypocrites) who say: “We believe in Allaah and the Last Day” while in fact they believe not. They (think to) deceive Allaah and those who believe, while they only deceive themselves, and perceive (it) not!… read more here.