C. F. Keil and Franz Delitzsch on Song of Solomon 4:5

Sol 4:5 5 Thy two breasts are like two fawns,    Twins of a gazelle,    Which feed among lilies.

The dual, originating in the inner differ. of the plur., which denotes in Heb. not two things of any sort, but two paired by nature or by art, exists only in the principal form; שׁדים, as soon as inflected, is unrecognisable, therefore here, where the pair as such is praised, the word שׁני is used. The breasts are compared to a twin pair of young gazelles in respect of their equality and youthful freshness, and the bosom on which they raise themselves is compared to a meadow covered with lilies, on which the twin-pair of young gazelles feed. With this tender lovely image the praise of the attractions of the chosen one is interrupted.

If one counts the lips and the mouth as a part of the body, which they surely are, there are seven things here praised, as Hengst. rightly counts (the eyes, the hair, teeth, mouth, temples, neck, breasts); and Hahn speaks with right of the sevenfold beauty of the bride.