Should he take a riba-based loan in order to get married?
Question

                I have been engaged for one year and seven months, and before that there was a relationship that lasted for one year and seven months. Until now I cannot afford the dowry and a little living expenses. My situation, by Allaah, is very critical and painful and because I have too many responsibilities on my shoulders and because I have no reliable source of income apart from the mercy of Allaah, I have no choice but to take out a marriage loan, because I can no longer bear to carry on like this and people are starting to talk which is causing me a great deal of anguish. By the way, as for my relationship with that girl, nothing has happened but that which is pleasing to Allaah and His Messenger. Allaah is a witness to what I am saying. Please note that I am the head of a family composed of six girls and two boys, and I have committed to sponsoring my brother through university.
Praise be to Allah.If the loan 
    you are asking about is a goodly loan that is to be paid off without paying 
    interest, then there is nothing wrong with you taking it, and may Allaah 
    help you to pay it off. The Prophet  (peace and blessings of Allaah be 
    upon him) said: “There are three who are promised the help of Allaah: the 
    mujaahid who is striving for the sake of Allaah, the slave who has a 
    contract of manumission which he intends to pay off, and the one who wants 
    to get married with the intention of remaining chaste.” Narrated by 
    al-Tirmidhi (1655), al-Nasaa’i (3120); classed as hasan by al-Albaani in 
    Saheeh al-Tirmidhi. 
And the 
    Prophet  (peace and blessings of Allaah be upon him) said: “Whoever 
    takes people’s wealth intending to pay it off, Allaah will help him to pay 
    it off, but whoever takes it intending to use it up (without repaying), 
    Allaah will destroy him. “ 
Narrated by 
    al-Bukhaari (2387). 
But if it is 
    a riba-based loan, in which repayment with interest is required, then it is 
    not permissible for you to take it, whether for the purpose of marriage or 
    anything else, because of the stern warnings which have been issued against 
    riba. For more information please see question no. 
    6847 and 
    9054. 
How can you 
    start your married life with something haraam? How can you receive divine 
    support when the one who engages in riba is threatened with a curse and is 
    subject to a declaration of war from Allaah and His Messenger? 
What you 
    have to do is to be patient and seek reward from Allaah, and wait for a way 
    out granted by Allaah; pursue the means that lead to halaal provision, and 
    do not pay attention to what people say. 
One of the 
    means of earning halaal provision is to buy something – a car or a house, 
    for example – by instalments, then sell it for cash to someone other than 
    the person from whom you bought it, even if it is less than the price to be 
    paid by instalments, so that you will have some money available. This is 
    called tawarruq, and is permissible according to the majority of scholars. 
See the 
    answer to question no. 45042. 
You made a 
    mistake by forming a relationship with this girl, no matter how much you say 
    that it was free of sin, because even if we assume that this is the case, it 
    still harms the girl because of keeping her hanging for such a long time, 
    when in fact you do not have the means to afford marriage. We ask Allaah to 
    forgive you and to bless you by His Bounty with that which will enable you 
    to obey and please Him. 
The Standing 
    Committee for issuing fatwas was asked about a man who did the marriage 
    contract but could not afford the mahr; can he take a loan from a riba-based 
    bank? 
They 
    replied: 
It is not 
    permissible for you to take this loan, and what you have mentioned about 
    your need for the mahr is not an excuse for taking a riba-based loan from 
    the bank or elsewhere. You have to fear Allaah, for “whosoever fears 
    Allaah and keeps his duty to Him, He will make a way for him to get out 
    (from every difficulty). And He will provide him from (sources) he never 
    could imagine. And whosoever puts his trust in Allaah, then He will suffice 
    him. Verily, Allaah will accomplish his purpose. Indeed Allaah has set a 
    measure for all things” [al-Talaaq 65:2-3]. We ask Allaah to make things 
    easy for you, to relieve your distress and grant you sufficient halaal 
    provision so that you have no need of anything haraam. 
End quote 
    from Fataawa al-Lajnah al-Daa’imah (13/387) 
And Allaah 
    knows best.