Al HaNissim
Al HaNissim is said on Shabbat and
not on Friday. On Sunday, it is not said
in davening or in Birkat HaMazon,
not even at the Purim seudah itself. If
one said it accidentally, one need not
repeat the Amidah. In fact, it is a good
custom to say Al HaNissim on Sunday
in מןָחֲרַה ָat the end of Birkat HaMazon.