I performed hajj tamattu' ('umrah followed by hajj), tawaf al-ifada (the going-forth circumambulation) and sa'y (going between Safa and Marwa) but forgot to shorten my hair. Is it obligatory to slaughter an animal in expiation?

The majority of scholars maintain that shortening the hair is an obligatory rite in hajj and 'umrah that necessitates slaughtering an animal in expiation if neglected.

The ruling

The petitioner must slaughter a sheep in expiation.
And God Almighty knows best.