Answered by Shaykh Faraz Rabbani
A person misunderstood the ruling for reciting silently when praying alone and never actually pronounced the fatiha in prayer for many years (they stood as one would behind an imam). since the sajda sahw was obviously never performed, do all of these prayers have to repeated?
Reciting the Fatiha is necessary (wajib), with the equivalent of 3verses of the Qur’an, in 2 rakats of the obligatory prayer. HOWEVER, reciting at least one verse of the Qur’an in two rakats is obligatory (fard).
If a wajib is missed, the prayer is valid but deficient and one would have to repeat the prayer to fix this deficiency, and seek Allah’s forgiveness for one’s shortcoming. Ignorance in religious matters is not an excuse, because one’s worship is more important than the dunya we are busy running after.
If a fard of the prayer is missed, then the prayer is not valid. As such, one would have to perform all such missed prayers, and seek Allah’s forgiveness…
The Expiation for Unperformed Prayers
And if one dies, an expiatory fine must be paid, by mentioning it in one’s will, for every single prayer missed (including the witr prayer), like the expiatory fine for each unperformed fast. This fine amounts to the monetary equivalent of 2.25 kg of wheat, in one’s country of residence.
This is not a joke. Since we don’t know whether we’ll live to fulfill our dues, we should have a recorded will where such things are kept track of, so if we die, such matters can be taken care of…