For he

"because he"

For he has broken the gates of bronze and cut through the bars of iron

Both of these phrases describe Yahweh freeing his people from prison and are used to emphasize that Yahweh truly freed them. AT: "He freed his people from prison" (See: rc://en/ta/man/translate/figs-parallelism and rc://en/ta/man/translate/figs-explicit)