Is it obligatory to repeat the prayers for someone who was unaware of the necessity of ghusl (ritual bathing) due to janabah (state of ritual impurity) and performed them in a state of impurity?

"Ghusl (ritual bath) from major ritual impurity (janabah) is a condition for the validity of prayer (salat), based on the Almighty's saying: 'And if you are in a state of janabah, then purify yourselves,' and the Prophet, peace and blessings be upon him, said: 'No prayer is accepted without purification.' Whoever prays while in a state of janabah without performing ghusl must repeat all those prayers, and ignorance is no excuse."