The wife asked her husband to “set me as a seal on your heart.” A person’s seal, here the seal of the king, was extremely important and personal. Jack Deere notes, “In Old Testament times a seal was used to indicate ownership of a person’s valued possessions. So the beloved asked to be the lover’s most valued possession” (“Song,” 1024).
She wants to be a seal, but one placed in a very particular and personal location: “on your heart.” In the ancient world it was often the custom to wear a signet ring or cylinder on a cord or necklace around the neck and near the heart. Schwab notes, “To be imprinted as a seal on another is to be inseparable from that person. She wishes his life to be hers” (“Song,” 426). For the king to love his lady in such a way that she felt near and dear to his heart would speak personally of his undying devotion and lasting love. As long as his heart beats, she wants to know and feel his love.
Believers in Jesus have a King who has set His seal on us, emblazoning it on our foreheads (cf. Rev 9:4) as a personal pledge of possession and protection. And we did not even have to ask. Indeed, through salvation provided for us in Christ, our God has “sealed us and given us the Spirit as a down payment in our hearts” (2 Cor 1:22). We have His seal on our foreheads and His seal in our hearts. We are “double-sealed” by our great Shepherd-King. The personal and intimate love He has for those who belong to Him is a pledge and promise we should never doubt.
— Daniel Akin, Exalting Jesus in Song of Songs, Kindle Location 3629.