Gregory of Nyssa on Song of Songs

Comment on Song of Songs 1:13...

The location of the heart is said by experts to lie between the two breasts. Here is where the bride says that she has the sachet in which her treasure is kept. Also, the heart is said to be a source of warmth from which the body's heat is distributed through the arteries. The body's members are thereby heated, animated and nourished by the heart's fire. Therefore the bride has received the good odor of Christ in the governing part of the soul and has made her own heart a kind of sachet for such incense. And so she makes all her actions, like parts of the body, seethe with the breath from her heart so that no iniquity can cool her love for God in any member of her body.

Homilies on the Song of Songs 3 in J. Robert Wright, Ancient Christian Commentary on Scripture: OT IX (Downers Grove: IVP, 2005), 306-307.