Psalm 68:27 goes on to mention the princes of Zebulun. Dwelling at the haven of the sea (Galilee) for a haven of ships (Gen. 49:13), Zebulun typifies Christ as the "haven" of the evangelists for the transportation and spreading in the preaching of God's gospel. The gospel has been accomplished, but there is the need of the spreading of the gospel by means of "ships." On the day of Pentecost, at least one hundred and twenty gospel "ships," all of whom were Galileans, set out to spread the gospel.
Finally, Psalm 68:27 speaks of the princes of Naphtali. Genesis 49:21 tells us that Naphtali is a hind let loose and that he gives goodly words.
Naphtali typifies Christ as the One who is released from death in resurrection, signified by the "hind let loose" (Psa. 22, title; S.S. 2:8-9), and gives goodly words for the preaching of His gospel (Matt. 28:18-20). In resurrection Christ came to His disciples and charged them to disciple the nations.
People of both Zebulun and Naphtali were men of Galilee (Matt. 4:12-17; Acts 1:11), from whom the gospel of Christ has been spread, preached, and propagated.
In typology Zebulun and Naphtali form a group for the spreading and the propagating of the glad tidings of Christ's redemption for God's salvation.
Perhaps you are wondering why only four of the twelve tribes of Israel are mentioned in Psalm 68:27. The reason is that in the typology here only four are required, and these four are the most suitable.
Just as the center of the first section of this psalm is the Triune God typified by the dove, the silver, and the gold, so the center of the second section is the four tribes of Benjamin, Judah, Zebulun, and Naphtali. The first two—Benjamin and Judah—are a group concerning the accomplishment and application of redemption; the other two—Zebulun and Naphtali—are a group concerning the preaching, spreading, and propagation of the gospel. As we consider the centers of the two sections of Psalm 68, we can see that the Triune God as Christ's spoil has become our enjoyment, and we can see also that Christ's redemption has been accomplished for God's salvation, that this accomplished redemption has been applied to us, and that the word concerning God's salvation is now spreading everywhere.