The Akeidah remembered every Rosh Hashanah

Yitzchak was thirty-seven at the Akeidah, and Chazal stress that a grown man could only be bound with his consent; he even asked his father to tie him well. That willing self-offering became a merit for all his children. The Gemara teaches that we blow a ram's horn on Rosh Hashanah because Hashem said: sound before Me a shofar of a ram, so that I will remember for you the binding of Yitzchak, and I will count it as though you had bound yourselves before Me. Rashi adds that the ashes of Yitzchak are always before Hashem, as if heaped upon the altar.