If I accidentally pray only 3 rakats for a 4 rakat Salah would I need to repeat the prayer
If you forget one of the essential parts of salah, such as a raka, and some time passes, and later you remember and know with certainty that your salah was deficient, then you must redo the salah.
References
- Related fatwa from the Qatari Fatwa Authority (Arabic PDF)
And God knows best.
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