This question has been debated among sincere Christians since Paul wrote Romans 9. Did Jesus die for only believers, or for all of humanity? I will state the case for Jesus dying only for believers by defining the word atonement (at-one-ment). An atonement is the satisfying of an offended party. It is the blotting out of offenses.
And the priest shall make an atonement for him with the ram of the trespass offering before the LORD for his sin which he hath done: and the sin which he hath done shall be forgiven him. [Lev 19:22]
When people offended God, an atonement was necessary to bring them back together. The atonement was never a nebulous transaction between unspecified parties, it was always specific in nature.
And Aaron shall offer his bullock of the sin offering, which is for himself, and make an atonement for himself, and for his house. [Lev 16:6]
On The Day of Atonement, an atonement was made for the children of Isreal only. The Amorites, Hivites, and Jebusites were excluded.
And Aaron shall lay both his hands upon the head of the live goat, and confess over him all the iniquities of the children of Israel, and all their transgressions in all their sins, putting them upon the head of the goat, and shall send him away by the hand of a fit man into the wilderness: [Lev 16:21]
Joshua was tricked by the wily Gibeonites, and made a treaty not to destroy them.
And Joshua made peace with them, and made a league with them, to let them live: and the princes of the congregation sware unto them. [Josh 9:15]Then there was a famine in the days of David three years, year after year; and David inquired of the LORD. And the LORD answered, It is for Saul, and for his bloody house, because he slew the Gibeonites. [2 Sam 21:1]
Saul broke a peace treaty that Isreal had made long ago with the Gibeonites, and now a famine came over the land. David then proceeded to satisfy the offended parties.
Wherefore David said unto the Gibeonites, What shall I do for you? and wherewith shall I make the atonement, that ye may bless the inheritance of the LORD? [2 Sam 21:3]
The price for the appeasement of the Gibeonites was seven of Saul's sons.
Let seven men of his sons be delivered unto us, and we will hang them up unto the LORD in Gibeah of Saul, [2 Sam 21:6]
The old covenant helps us understand new covenant teachings.
For whatsoever things were written aforetime were written for our learning, [Rom 15:4]
Jesus compares himself to the sacrificial animals of the old covenant, and the high priests that offered the sacrifice as well.
For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself. [Heb 7:26-27]
Further proof of this is found in the fact that Jesus was the fulfillment of the Old Testament.
Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill. [Matt 5:17]
It is as if Jesus says, "all the law and the prophets point to me, and I will fulfill in every detail". Just as the atonements of the old covenant were for specific people, the atonement of Jesus in the new covenant was for specific people as well. Jesus died not for the masses in hell, but for believers only.
And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins. [Matt 1:21]I am the good shepherd: the good shepherd giveth his life for the sheep. [John 10:11]
If Jesus did die for those in hell, what confidence would I have that I would not end up there also? If Jesus died for more than believers, we then need to find a doctrine to explain why some of those for whom He died are in hell. If some sheep are in hell, then Jesus did not
perform the good work until the day of Jesus Christ [Phil 1:6]
that he said he would! Or, can one really loose their salvation as many denominations teach? God forbid!