Like to a palm tree - Which is remarkably straight, taper, and elegant.
And thy breasts to clusters of grapes - Dates are the fruit of the palm tree; they grow in clusters; and it is these, not grapes, which are intended.
Matthew Henry
Concise Bible Commentary
The similitudes here are different from what they were before, and in the original refer to glorious and splendid clothing. Such honour have all his saints; and having put on Christ, they are distinguished by their beautiful and glorious apparel. They adorn the doctrine of God their Saviour in all things. Consistent believers honour Christ, recommend the gospel, and convince and awaken sinners. The church resembles the stately and spreading palm; while her love for Christ, and the obedience resulting therefrom, are precious fruit of the true Vine. The King is held in the galleries. Christ takes delight in the assemblies and ordinances of his people; and admires the fruit of his grace in them. When applied to the church and to each faithful Christian, all this denotes that beauty of holiness, in which they shall be presented to their heavenly Bridegroom.