The Early Church Fathers taught that those outside of the Catholic Church had no hope of salvation. That is, if they heard the gospel and knowingly rejected it. However, they made an allowance for those who, through no fault of their own, didn't know any better. They didn't see God as being legalistic. Rather they saw a merciful God who judged men by what they did with what they had.
Salvation comes from God alone; but because we receive the life of faith through the Church, she is our mother:
"We believe the Church as the mother of our new birth, and not in the Church as if she were the author of our salvation."
— Faustus of Riez, De Spiritu Sancto 1,2: PL 62,II.
Because she is our mother, she is also our teacher in the faith.
The Church's Scriptures that deals with Salvation outside the Catholic Church:
Jesus, Himself, preaching the Good News states:
16 He who believes and is baptized will be saved; but he who does not believe will be condemned.
Mark 16:16
Baptism necessary for salvation
5 Jesus answered, "Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God."
John 3:5
Paul teaches us in men will be judged by the purposes of their hearts.
5 Therefore do not pronounce judgment before the time, before the Lord comes, who will bring to light the things now hidden in darkness and will disclose the purposes of the heart. Then every man will receive his commendation from God.
1 Corinthians 4:5
Faith is necessary to please God
6 And without faith it is impossible to please him. For whoever would draw near to God must believe that he exists and that he rewards those who seek him.
Hebrews 11:6
