Shaykh Saalih Al-Fawzaan was asked
From the conditions of the marriage contract, is it necessary to have it written [i.e. Writing the contract]?
“No, writing [the marriage contract] is not from the conditions for the validity of the marriage. If there is the agreement of the Wali (the guardian) and the acceptance of the groom or from their Wakeels [i.e. Trustees], in the presence of two just witnesses, along with the removal of any preventatives from the two spouses, then the contract is valid even if it is not written. Yes”.
Faisal bin Abdul Qaadir bin Hassan