As for the textual evidence, it is the general wording of the Messenger of Allah’s statement: “Let no one propose over his brother’s proposal.” (1) This includes the case in question. Hence, another narration states: “Unless he gives permission or she rejects him.” (2)
As for rational consideration, this leads to enmity and cuts off another’s provision. The Prophet said: “A woman must not ask for her sister’s divorce in order to empty what is in her bowl.” (3) Thus, if you propose while not knowing whether he has been accepted or rejected, this means that you have cut off his provision.
If we say that it is not permissible to propose over one’s brother’s proposal, how do we answer the account of Fatimah bint Qays, when she came to consult the Prophet after three men—Abu Jahm, Mu'awiyah, and Usamah—had proposed to her? (4)
The answer is that this account is to be understood as meaning that none of them knew of the others’ proposals.
It is recommended to conclude the marriage contract on Friday evening, ………
His words, “It is recommended to conclude the marriage contract on Friday evening,” mean that it is recommended to conclude the marriage contract on Friday evening—that is, after the afternoon prayer. Ibn al-Qayyim mentioned that it should also be done in the mosque, due to the nobility of both the time and place. However, this is open to question in both respects, unless an established sunnah proves it, in which case it would be binding.