"God's word" here is a metonym for the message from God. AT: "those who instructed you in what God has said" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here the trust in God and the way of life led by these leaders are spoken of as "their faith." AT: "Trust and obey God in the same way they do" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here "yesterday" means all times in the past. AT: "is the same in the past, the present, and in the future forever" (See: [[rc://en/ta/man/translate/figs-metonymy]])