Did Jesus teach that there were multiple ways to receive eternal life? No, Jesus did not teach universal salvation, he makes it very clear that we must submit to him since he is the king of heaven and earth and he is the only one that provides the power to overcome sin. Jesus explains this in John 3:16-21, in verses 16-17 he says those that believe are saved. In verses 18-19, he talks about the condemnation of nonbelievers on judgment. Lastly, in verses, 20-21 he explains why things are set up this way, and that is because receiving salvation is like stepping into the light, and rejecting it is staying in darkness. He explains that (NLT) John 3:20 “all who do evil hate the light and refuse to go near it for fear their sins will be exposed. 21 But those who do what is right come to the light so others can see that they are doing what God wants.” Jesus says in his parable of the wedding banquet that people who refuse the banquet invitation (salvation offer) will be cast into outer darkness (Matthew 22:1-14). In both Matt 25:31-46, as well as in the parable of the wheat and weeds/tares (Matt 13:36-43), Jesus distinguishes between righteous and unrighteous. The unrighteous are always cast into darkness on judgment day (Matthew 8:12, Matt 22:13, Matt 25:30).
In John 12:44-50 Jesus says everything he teaches comes from the Father, and that anyone that rejects his teaching will be judged, but those who followed it will be delivered from the darkness. In Mark 16:15-16 Jesus gives the great commission and said those that believe and are baptized will be saved, but those that don’t will be condemned. In John 6:60-71 Jesus says the spirit alone gives eternal life and human effort accomplishes nothing, and that his words are “spirit and life”. Some disciples abandoned him because they stopped believing, leaving only the 12, and Jesus said “only those whom the Father gives to him are his”.
In John 17:1-21 Jesus prays a prayer that makes it clear that only the ones God gave to him will inherit the kingdom. He isn’t praying for the world, but for the sheep that God gave him (v9-10). Jesus also says that God’s true sheep were always his (v6). In v13-16 he says God’s people are in the world but are not of this world, and that the world hates them. In v22-24 he says that he wants the world to know that God loves the believers (the ones God gave him) as much as he loved Jesus, and God wants for them to be with him where he (Jesus) is so that they can see his glory and all God has given him because God loved him before the world began. In v25-26 Jesus says the world doesn’t know God but his disciples know God sent Jesus and believed in him, and that Father’s love for Jesus will be in them (the believers) as well. This continues what John 3:16-21 teaches, which is that only the ones who believe in God’s son will inherit eternal life. Everyone else will be judged and condemned because they loved sin more than God.
Also, John 10:1-21 talks about Jesus as the good shepherd. Jesus says he is the true shepherd and that his true sheep only follow him and not the voice of thieves and strangers (v8-10). He compared Israel’s leaders to hired hands who run when danger comes and don’t care about the sheep in their care and would flee at the sign of danger (like a wolf). Unlike them, Jesus cares for the sheep and will give his life for them (v11-13). He also makes it clear that he died specifically for the sheep (v15), and that Gentiles are included along with Jews in the new sheepfold (v16). In verses 19-21 the people are divided, some believe he is demon posses and a heretic and others believe he is a man of God. The division represents everything he was talking about, those that received his message in faith are his sheep, and those that didn’t receive him are not his sheep.
Paul says that God knew his people in advance and chose them to be like his son (Rom 8:29-30). In Romans 9 Paul contrasts the chosen remnant of people in the new covenant with those in the old covenant. He points out how God selected specific descendants of Abraham (Isaac) and Isaac (Jacob) over their siblings. His point is that being a descendant of Abraham didn’t guarantee salvation, and like Jesus said only some (his sheep) will be saved.
Hebrews 4:1-7 says those that believe God’s word will receive his promise of salvation and enter his rest, but everyone else will be restricted from entering his rest, and believers are warned not to harden their hearts like the Israelites. This is comparable to the oath God took against the rebellious Israelites, that they will never enter God’s rest (Ps 95:7-11, Heb 3:7-11) because of their rebellion in the wilderness (Num 14:26-45). In Heb 10:35-39, it says that only people in faith are considered righteous and will be saved but God takes no pleasure in those that draw away from him, and they will be turned away to their own destruction.
God always selected a remnant of people in judgment going all the way back to the flood, where Noah and his family and the animals he brought in the ark were spared among all those living on land (Genesis 6-9). Also in Sodom and Gomorrah where only Lot, Abraham’s nephew was spared because there was no one else righteous among them (Genesis ch.19). Among the Canaanites in Jericho, Rahab the prostitute was spared for protecting Israelite spies (Joshua ch2, & 6:17-25) and was counted as righteous (James 2:25, Heb 11:31), even making it into the lineage of Jesus after marrying Salmon (Matt1:5). Revelation 20-22 makes a clear distinction between those willing to serve God and those who rebel against God.
There’s no universal salvation taught in scripture. Only a remnant of humanity that belong to God as his sheep, which are those that know his voice, will be saved on Judgement day. To join in the new covenant one must receive the gospel by confessing and believing that Jesus is Lord, according to Romans 10:8-21.