Albert Barnes Commentary Song Of Solomon 8:6-7

"Set me as a seal upon thy heart, As a seal upon thine arm: For love is strong as death; Jealousy is cruel as Sheol; The flashes thereof are flashes of fire, A very flame of Jehovah. Many waters cannot quench love, Neither can floods drown it: If a man would give all the substance of his house for love, He would utterly be contemned." — Song Of Solomon 8:6-7 (ASV)

The bride says this as she clings to his arm and rests her head on his bosom (John 21:20). This brief dialogue corresponds to the longer one in Song of Solomon 4:5–7:1, on the day of their wedding.

Allegorical interpreters find a fulfillment of this passage in the close of the present age: the restoration of Israel to the promised land and the manifestation of the Messiah to His ancient people there, or His Second Advent to the Church.

The Targum interprets Song of Solomon 8:6 as a prayer by Israel, after being restored to the holy land, that they may never again be carried into captivity. It sees Song of Solomon 8:7 as the Lord’s answering assurance that from that time on, Israel is safe (Isaiah 62:3–4).

Song of Solomon 8:6 is the keynote of the poem. It serves as the Old Testament counterpart to Paul’s celebration of love in 1 Corinthians 13:1–13.

• Love is presented here as a universal power, an elemental principle of all true being. It alone is able to contend with the two eternal enemies of God and humanity: Death and his kingdom, Sheol. As the verse says: For strong as death is love,
  tenacious as Sheol is jealousy. In this context, “jealousy” is another term for “love,” expressing the relentless force and passion of this affection, which can neither surrender nor share possession of its object. In the mind of the sacred writer, it is identified with divine or true life.
• The author goes on to describe love as an all-pervading fire, kindled by the Eternal One and partaking of His essence: Its brands are brands of fire,
  a lightning flash from Jah. .
• This divine principle is next shown to be so powerful that it overcomes all opposing forces, which are symbolized by water.
• Therefore, it follows that love, even as a human affection, must be revered. It cannot be bought with anything of a different nature, for any such attempt only awakens scorn.