The 59th prohibition is that we are forbidden from forgetting what the descendants of Amalek did to us, i.e. to be the first to attack us [after we were redeemed from Egypt].

In P189 we explained that remembering what the descendants of Amalek did to us and constantly renewing our hatred towards them is a positive commandment. Similarly, we are forbidden from ignoring it and forgetting about it, and it is an actual prohibition.

The source of this prohibition is G‑d's statement,1 "Do not forget."

The Sifri2 says, " 'Remember,' means verbally. 'Do not forget,' means in one's heart." This means that you should not ignore hating him, nor remove it from your heart.