en_tn_condensed/1sa/17/55.md

When Saul saw David

"When Saul had seen David". This (17:55-56) happened before David killed Goliath.

go out against the Philistine

"go to fight against the Philistine"

whose son is this youth

"who is this youth's father"

As you live

This was a way of swearing that what he was about to say was true.