What is the ruling on slight swaying while standing in prayer, whether due to forgetfulness or intentionally, and is prostration of forgetfulness (sujood al-sahw) required in both cases, and what is the ruling on previous prayers if the reason for the swaying was forgotten?

If swaying means alternating between the feet during prayer, then there is no harm in it, especially with prolonged standing. It is recommended by the Hanbalis and disliked by the majority. However, if it means rocking the body right and left or forwards and backwards, then this is disliked and resembles the action of the Jews. Excessive movement of this kind may invalidate the prayer.