Many loans fail to be repaid properly and promptly because of diversion; i.e using it for purposes other than for which it is borrowed.
Earlier days banks used to lend only for productive purposes and buying assets other than land. Personal loans were given for buying appliances and assets use for daily convenience. But the bill and receipt for having purchased them were insisted upon to ensure that the money borrowed was used for the intended purpose. Even physical inspections were carried out.
But later on banks started giving loan s for even social spending and personal consumption. No questions were asked as to what purpose it is used for. Todays' personal loans are thus purely 'for personal consumption purposes'.
So in this case in the above question, even if it was for marriage purpose, bank may not ask for any proof of spending. Once the lending bank sends the money to your bank account the loan is given and you are bound to repay as per agreement.
But in your case I guess it may not be bank loan, but sourced from non-banking sources.
In any case, if you feel it is okay to use the money for some other legally allowed purpose, then it is your responsibility. But you should not default the scheduled repayment.
If the money is borrowed legally then there is no problem transferring it via banking channels paying the required charges and identification like PAN no. Aadhaar card etc. Non cash transactions properly routed through banks are now welcome and encouraged.
Now the practical and ethical question.
If you buy land with the borrowed money, how will you conduct the marriage? Will it not cause disappointment to the person(s) concerned? The priority is to be decided by you only. Have you a real repayment capacity meeting both marriage and land buy? Work out and decide.