en_tn_condensed/1sa/02/35.md

I will raise up ... a faithful priest

This is an idiom. Alternate translation: "I will cause a man to become priest" (See: rc://en/ta/man/translate/figs-idiom)

for myself

This is an idiom. Alternate translation: "to serve me" (See: rc://en/ta/man/translate/figs-idiom)

what is in my heart and in my soul

"what I want him to do and what I tell him to do"

I will build him a sure house

Here "house" is an idiom used for "descendants." Alternate translation: "I will ensure that he always has a descendant who serves as high priest" (See: rc://en/ta/man/translate/figs-idiom)