Affection, especially public displays of affection in the eastern societies, are divided into two categories as this verse makes clear:
- sibling, familial and friendship affection such as between brothers and sister or between mother and children, or between close friends, etc. This kind of familial affection in public is encouraged and condoned.
- affection with sexual overtones such as between married people in public is strongly discouraged. It would be very rare to see a husband and wife kiss in public and if it did occur, it would be frowned upon.
Thus, in the Song of Solomon, the woman wishes to express here love and affection for the man by kissing but because of her strong (sexual) desires for him (SS 2:7, 3:5, 8:4, see also SS 2:5, 5:8), must refrain from doing so.
Note the comments of Benson -
Song of Solomon 8:1. O that thou wert as my brother — Most
intimate, and free, and familiar with me, as brethren and sisters
commonly are; ... When I should find thee without, &c. — In the open
streets; I would kiss thee, &c. — And thus express my affection to
thee openly, without fearing any scandal or contempt; such expressions
being usual among persons so nearly and dearly related.