I think it is in Matthew we read that we should not cause another to sin. Are we responsible for our own salvation? Or can we be held responsible someday for causing another to sin and which kept them out of heaven?
"But whoever causes one of these little ones who believe in Me to sin, it would be better for him if a millstone were hung around his neck, and he were drowned in the depth of the sea" (Matthew 18:6).
Each person is ultimately responsible for his own decisions. "The soul who sins shall die. The son shall not bear the guilt of the father, nor the father bear the guilt of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself" (Ezekiel 18:20). But that also includes what that person teaches another person. "My brethren, let not many of you become teachers, knowing that we shall receive a stricter judgment" (James 3:1).
If a person teaches another person false doctrine to cause them to be lead astray. The false teacher is held responsible to leading him astray, but the person is also responsible for following a false teacher. "Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world" (I John 4:1).
What Jesus said is that God is going to be particularly angry with a false teacher who takes advantage of a person's youth or newness in faith to convince them to believe a lie. The person, though young in faith, is still responsible for what he does -- he does have to grow up. But Jesus says God is going to come down particularly hard on those who make things hard on the young in faith.
"Therefore, my beloved, as you have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling; for it is God who works in you both to will and to do for His good pleasure" (Philippians 2:12-13).