The first word of dialogue or of a quote is always capitalised, unless it is just a clause, phrase or word that is used as part of your bigger sentence (i.e. is a woven quote or an integrated quote), e.g.
My mother warned me that “crocodiles prefer older siblings to younger siblings.” (The use of the word that here makes this quote woven/integrated)
My mother says that crocodiles’ teeth are “hideous.”
https://www.grammarbook.com/punctuation/quotes.asp