Is the offering made by both the one performing Hajj solely (Mufrid) and the one performing Hajj and Umrah together (Qarin) obligatory or voluntary?

The Hady (sacrificial animal) is not obligatory for someone performing Hajj Ifrad (Hajj alone); rather, it is recommended for them, and it falls under the category of voluntary acts. As for the Qarin (one who performs Hajj and Umrah together), one Hady is obligatory for him, and if he slaughters more than one Hady, it is an act of obedience for which he will be rewarded. The Hady is an act of closeness and obedience to Allah Almighty, whether it is obligatory, such as the Hady for Tamattu' (Hajj and Umrah together with a break in between) and Qiran, or voluntary. The time for voluntary sacrifices is wide and encompasses all times.