Answer: The marriage contract according to the Sunnah is that a guardian must be present; for it is reported in the Sunan from Abu Musa, from the Prophet (peace and blessings of Allah be upon him and his family), that he said: "There is no marriage except with a guardian."
And the woman being proposed to must be consenting; for the Prophet (peace and blessings of Allah be upon him) says: "The previously married woman is consulted, and the virgin is asked for permission; and her permission is her silence." So, it is necessary that she is consenting, and if she is not, then the contract is invalid - except if she is young and has not reached maturity, in which case it is permissible for her father to marry her off, as Abu Bakr married off Aisha to the Prophet (peace and blessings of Allah be upon him), and it was not reported that he consulted her. Therefore, if she is young, there is no harm in her father marrying her off, and if she reaches maturity and the husband is not suitable, she is allowed to annul the marriage. It was narrated that Khansa bint Khidam - or someone else - came to the Prophet (peace and blessings of Allah be upon him) and said: "O Messenger of Allah, my father married me to his nephew to elevate his status by me." The Prophet (peace and blessings of Allah be upon him) annulled her marriage. She then said: "O Messenger of Allah, I have approved of what my father did, but I wanted to show the women that they have a right."
We said: A guardian, the consent of the woman being proposed to, and then after that, two witnesses. It seems that the two witnesses are not a condition for the validity of the contract, as the hadith "There is no marriage except with a guardian" is authentic, and the wording regarding "two witnesses" should be examined.
After that, you say to the guardian: "O so-and-so, have you married your daughter, so-and-so, to so-and-so?" And you name her, because perhaps he has daughters, and some are desired, while others are not. He then says: "I have married her." The groom, the suitor, also says: "I accept." If you recite the verses mentioned and the Khutbat al-Haja, it is better. As reported in Sunan Abi Dawood from Abdullah bin Mas’ood, the Prophet (peace and blessings of Allah be upon him) used to say in the Khutbat al-Haja: "Indeed, all praise is due to Allah. We praise Him, seek His help, and seek His forgiveness. We seek refuge in Allah from the evils of our souls and from our bad deeds. Whomsoever Allah guides, none can misguide, and whomsoever He misguides, none can guide. I bear witness that there is no deity worthy of worship except Allah, alone without any partner, and I bear witness that Muhammad is His servant and Messenger.
'O you who have believed, fear Allah as He should be feared and do not die except as Muslims' (3:102). 'O mankind, fear your Lord, who created you from one soul and created from it its mate and dispersed from both of them many men and women. And fear Allah, through whom you ask one another, and the wombs. Verily, Allah is ever, over you, an Observer' (4:1). 'O you who have believed, fear Allah and speak words of appropriate justice. He will amend for you your deeds and forgive you your sins. And whoever obeys Allah and His Messenger has certainly attained a great attainment' (33:70-71).
Then you say: 'O so-and-so, have you married your daughter, so-and-so, to so-and-so?' He says: 'I have married her.' And the suitor says: 'I accept.'
As for the dowry, it may be specified and agreed upon, and if it is not specified, it is permissible for it to be based on the customary dowry. It is recommended to be lenient with the suitor. From this, it is understood that Khutbat al-Haja is not obligatory.