en_tn_lite_do_not_use/isa/07/09.md

the head of Samaria is Remaliah's son

This means Pekah is the king of Samaria and all of Israel. AT: "the king of Samaria is Pekah, who is a weak man" (See: rc://en/ta/man/translate/figs-explicit)

If you do not remain firm in faith, surely you will not remain secure

This can be stated in positive form. AT: "If you continue to believe in me, you will certainly remain safe" (See: rc://en/ta/man/translate/figs-doublenegatives)

If you do not remain

"Unless you remain"