The abstract noun "guarantee" can be stated with the verb "promised." Alternate translation: "For I promised my father concerning the boy" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
Being considered guilty is spoken of as if "guilt" were something that a person carries. Alternate translation: "then my father may blame me" (See: [[rc://en/ta/man/translate/figs-metaphor]])