"Where in scripture does it tell us to interpret scripture?"
The problem was already 4000 years old by the time the NT was written. The Torah was origionally written WITHOUT vowles, upper and lower case, and punctuation. Consider:
From “The Way Into Torah,” Norman J. Cohen:
. . . the Divine Word. Each and every person heard it according to his or her own capacity. Thus David said, “The voice of the Lord is in the strength” (Psalm 29:4). [The Biblical does] not say, “The voice of the Lord is in His [meaning God's] strength” [which is what we would expect], but rather, “The voice of the Lord is in [the] strength” [and capacity] of each and every person. . . .
. . . Similarly, in the final section of this passage, the Rabbis find an unusual detail in the language of the biblical text and fine-tune its meaning for their own purpose. The simple understanding of the phrase from Psalm 29:4, “The voice of the Lord in the strength,” is that “the strength” refers to God's strength. But since the verse has no possisive, and therefore does ot make this explicit, the Rabbis feel free to read it as if it meant “The voice of the Lord is in the strength [or each person].” The Rabbis are able to read the Torah text in their own way because they themselves are attentive readers.
My point – and Cohen's point? - is that the saying (oral Torah) could have been made before the Masoratic text was established and in any event if one is to claim “Bible only” then Masorites had to have been as inspired as Moses.