For an Islamic marriage to be sahih (valid), both the groom and the bride have to be Muslims. That is, they have to know and believe the tenets of belief (iman)  and Islam. If there is doubt concerning their iman, the person who will perform the nikah  , after saying the Basmala  , the (prayers of) hamd  and salawat  , mentions the six tenets of iman and the five principles of Islam one by one and has the groom and the bride say them, too. Then he states the Sifat-i-dhatiyya and the Sifat-ithubutiyya of Allahu ta’ala, the important attributes of Prophets and angels, the teachings pertaining to grave and the Hereafter, respectively, and has them repeat. He has them say, “We believe, we have iman,” “I am a Believer, I am a Muslim.” Then he must perform the nikah, beginning with the groom or his wakil (proxy). It is stated as follows in Radd-ul-mukhtar: “When both the woman and the man are present, it is not permissible for them to perform the nikah by writing. When they are not together, it is permissible for one of them to send a letter and the other read the letter in the presence of two witnesses and accept it orally. It is not permissible if both parties state their parts in written form. The woman reads or explains the letter she has received from the man to two witnesses and says, ‘Be my witnesses! I have accepted to be his wife.’ The woman’s reading the letter to the witnesses is equivalent to the man’s proposing orally in the presence of the witnesses.”
 iman: faith, belief, beliefs of Islam; kalam, i’tiqad.
 nikah: Islamic act of engagement for marriage.
 basmala: the phrase “Bismi’illahi ‘r-rahmani ‘r-rahim” (In the Name of Allahu ta’ala the Compassionate, the Merciful).
 hamd: glory, glorification; gratitude and praise. : thanksgiving
 salawat: (pl. of salat) special prayers in which blessings and high ranks are invoked on the Prophet (‘alaihi ‘s-salam).