The Douay Rheims says
3:15 But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth.
For your information the word “the” which is a definite article translated from the Greek transliterated word “ho” does not appear in the verse anywhere. Therefore, to place the definite article before pillar is incorrect and is at best a most arbitrary translation. The word “church” is translated from ekklesia which has a Greek meaning of OUT-CALLED or in English we say ecclesia or congregation. The congregation generally means an assemblage of persons, whereas Church is clearly an institution. Young’s Literal Translation says
and if I delay, that thou mayest know how it behoveth thee to conduct thyself in the house of God, which is an assembly of the living God – a pillar and foundation of the truth,
The assembly (or church) of the living God is in apposition to the expression “house of God in both translations. The assembly and house are in the same syntactical relation whereas the next part of the verse “a pillar and foundation of the truth” is clearly admonition to Timothy as to how to “behave thyself or conduct thyself” in view of the context of the entirety of chapter 3 preceding this verse.
In your original statement “the bible calls the church the fountain of truth which can not teach error.” The word fountain is completely wrong as the Greek word “hedraiOma” means “settle, or base or foundation.” Never does it mean fountain.
