What is entailed for someone who was unaware of the necessity of washing the heels (ʿaqibayn) during ablution and prayed many prayers, and is he required to repeat them?

The feet, including the heels, must be washed up to the ankles during ablution (Wudu'). If one leaves any part unwashed, their ablution is invalid, just as if they left a fingernail's breadth unwashed on their feet. The Prophet, peace and blessings be upon him, said: "Woe to the heels from the Fire." And it is narrated from Umar ibn Al-Khattab, may Allah be pleased with him, that a man performed ablution and left a fingernail's breadth unwashed on his feet. The Prophet, peace and blessings be upon him, said to him: "Go back and perfect your ablution." Therefore, whoever prays with an invalid ablution must repeat their prayers, according to the majority of scholars. However, Shaykh al-Islam was of the opinion that one is not required to repeat prayers if they missed a condition or pillar due to ignorance, but the opinion of the majority is more cautious.