Sierra siempre nos la dice.
To replace the accompanying noun, write a direct object. They can be replaced if it is masculine it is "lo" (singular) or "los" (plural) and if it is feminine it is "la" (singular) or "las" (plural).
The indirect object replaces the one who receives the verb. It can be replaced, if it is in the third person, "le" (singular) or "les" (plural); they can also be replaced by unstressed pronouns (me, se, te, nos, os).
When a direct object and an indirect object are joined, the indirect object must be put first and then the direct object. When a third person indirect object is added, put "se".
In this case the indirect object is "nos" because the verb falls to us and the direct object is "la" because it replaces "la vardad" (the truth).
MissSpanish