Many people say there is only one way to Heaven by accepting Jesus Christ as personal Savior, but then they default to several other ways (young age, mental illness, being born in Israel, keeping sacrificial requirements of the law) and make excuses when cornered. Is believing in Jesus really the ONLY way?
Christians who believe the Bible is the infallible Word of God must also believe Jesus is the only way to a reconciled relationship with God (and therefore eternal life). There are many Bible verses that teach this (John 8:24; Acts 4:12; 1 Timothy 2:5 and more), the most well-known being John 14:6, "Jesus said to him, ‘I am the way, and the truth, and the life. No one comes to the Father except through me.’"
When it comes to those who lack the mental capacity to accept Jesus, evangelical Christians believe different things. Some believe that death in infancy or having a mental illness is a sign of special election by God, assuring his or her salvation. Others believe Jesus' death on the cross covered the guilt of original sin, so only people who knowingly rebel against God (which is only possible if you are also able to knowingly accept him) are responsible for their personal sins and therefore without then reconciling to God through Jesus will not be saved. Still others believe families can be seen as a spiritual unit. They believe that if a child is born to Christian parents and then dies, that child will be saved through his or her parents' salvation.
The bottom line is that the Bible doesn't give us a straight-forward answer to this very important and highly emotional question, but it does tell us that we can trust God who is abounding in mercy, compassion and love to do what is right and good, for he did not even spare himself from suffering and death on the cross to bring salvation to his creation.
Regarding Israel, earlier in Romans Paul wrote, "... For not all who are descended from Israel belong to Israel, and not all are children of Abraham because they are his offspring...This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as offspring." (9:6-8). So Paul had previously specified that being an ethnic Jew was not enough to achieve salvation. Personal faith is the basis of salvation. However, Romans 9-11 does seem to imply there is still some sort of special role for Israel in God's redemptive history and its own salvation, but it's debated among Christians what that is specifically.
Addressing your last point, Hebrews 10:4 says: "For it is impossible for the blood of bulls and goats to take away sins." Men and women have never been saved by their sacrifices but by their faith. Genesis 15:6 says, "And [Abram] believed the LORD, and he counted it to him as righteousness." Paul cites this verse in his letter to the Romans as evidence that no man is saved by works (e.g. sacrifices), but faith (Romans 4:1-8). The sacrifices of the Old Testament were a way for God to reveal himself to his people, teach them the consequences of sin, the difference between life and death, and give them an opportunity to show their love for him through loving obedience and faithfulness. The sacrifices also pointed to the coming Messiah who is Jesus. He is the true and ultimate sacrifice for the atonement for Jew and Gentile alike.
Julia (Stager) Mayo holds a Master of Arts in Biblical and Theological Studies from Western Seminary. She was previously part of the Eternal Perspective Ministries staff, and still does occasional research work for Randy Alcorn.