To become a Muslim one must simply pronounce the Shahaadatayn (Declaration of Faith) with sincerity and conviction.
The Shahadah can be declared as follows:
"ASH-HADU ANLA ELAHA ILLA-ALLAH WA ASH-HADU ANNA MOHAMMADAN RASUL-ALLAH".
The English translation is:
"I bear witness that there is no deity worthy to be worshiped but Allah, and I bear witness that Muhammad is His servant and messenger."
The Shahadah is the dividing line between unbelief (kufr) and Islam. It is also called the kalimah (word). Whoever says it with truthfulness will enter the Gardens of Paradise
It is [a kalimah] that Allah Himself has testified to, as have the angels and those who possess knowledge from amongst His creation. Allah the Most High said:
"Allah bears witness that none has the right to be worshiped except Him; as do the angels and those who possess knowledge. He maintains His creation upon justice. None has the right to be worshiped except Him, the All-Mighty, All-Wise."
[Soorah Aal-Imraan 3:18]
It is a concise declaration that contains few letters; light upon the tongue, yet heavy in the scales.
Prophet sallallahu alaihi wasallam, who said: "A person from my ummah will be summoned in front of everyone on the Day of Resurrection. Ninety-nine scrolls will be unfurled for him, each scroll extending as far as the eye can see. Then it will be said: Do you deny any of this [i.e. your bad deeds]? So the man will reply: No, 0 Lord.
Then it will be said: Do you have any excuse or any good deed? The man, in a state of terror, will answer: No. It will then be said: Rather, you do have some good deeds and no injustice will befall you this Day. So a parchment will be taken out for him, upon which there will be the testification of laa ilaaha illallaah and the testification that Muhammad is the Slave and Messenger of Allah.
The man will say: 0h Lord, what is this parchment in comparison to those scrolls! It will be said to him: No injustice shall befall you. The scrolls will then be placed in one of the scales and the parchment in the other; the scrolls will be light in weight, whereas the parchment will be heavy." ( Reported by at-Tirmidhee (no.2641), from Abdullaah ibn Amr radhiyallahu anhu. It was declared to be saheeh by Shaykh al-Albaanee in as-Saheehah (no.135).
The first part of the Shahadah is laa ilaaha illallaah (none has the right to be worshiped except Allah) and the first part if the Shahadah has two pillars:
The first pillar is the pillar of negation (nafee), whilst the second is the pillar of affirmation (ithbaat). What is meant by negation is to negate divinity and worship (ilaahiyyah) for anything except Allah, the Most High. What is meant by affirmation is to affirm divinity and worship only for Allah the Most Perfect; for it is He alone that is the true Deity. So whatever else is taken by the unbelievers as deities to be worshiped are in fact all false and futile: That is because Allah is the true Deity to be worshiped, and whatever else they invoke besides Him is vain falsehood.
[Soorah al-Hajj 22:62]
