Answer:
(Fatwa: 1481/1483/M=1430)
It is necessary to do taubah (seeking forgiveness from Allah with firm intention not to repeat the action in future) for repentance from the sin of adultery, not for validity of marriage. If someone marries with a girl with whom he had illegal sexual relation, the nikah will be valid even without taubah if it was solemnized in proper way i.e. with witnesses and without any matter preventing between the two.
Ask the Maulana for proof who said that marriage without taubah is invalid or ask him to write down what he exactly said.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
