Thy lips are like a thread of scarlet, and thy speech is comely: thy temples are like a piece of a pomegranate within thy locks.
Thread - like a delicate fillet. Not thick and white as the leper's lips (type of sin), which were therefore to be 'covered' as "unclean."
Scarlet - the blood of Jesus Christ (typified by the live coal from off the altar applied to Isaiah's lips by the seraph, Isaiah 6:5; Isaiah 6:9) cleanses the leprosy and unseals the lips (Hebrews 13:15). Rahab's scarlet thread was a type of it.
Speech - not a separate feature from the lips (Colossians 4:6). Contrast "uncircumcised lips," Exodus 6:12. Midbar (H4057) elsewhere means a wilderness; here only speech.
Temples - rather, the upper part of the cheek next the temples; the seat of shamefacedness: so, "within thy locks" (Song of Solomon 4:1); no display (1 Corinthians 11:5-6; 1 Corinthians 11:15). Mark of true penitence (Ezekiel 16:63). Contrast Jeremiah 3:3, "a whore's forehead;" Ezekiel 3:7, "impudent;" Hebrew, stiff of forehead.
Pomegranate - when cut, it displays in rows seeds pellucid, like crystal, tinged with red. Her modesty is not on the surface, but within, which Jesus Christ can see into.