A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 128:1The temporal blessings of true piety. The eighth chapter of Zecariah is a virtual commentary on this Psalm. Compare Psa 128:3 with Zac 8:5; and Psa 128:2 with Lev 26:16; Deu 28:33; Zac 8:10; and Psa 128:6 with Zac 8:4. (Psa 128:1-6)
(Compare Psa 1:1).
psa 128:2For thou shalt eat--that is, It is a blessing to live on the fruits of one's own industry.
psa 128:3by the sides--or, "within" (Psa 48:2).
olive plants--are peculiarly luxuriant (Psa 52:8).
psa 128:5In temporal blessings the pious do not forget the richer blessings of God's grace, which they shall ever enjoy.
psa 128:6Long life crowns all other temporal favors. As Psa 125:5, this Psalm closes with a prayer for peace, with prosperity for God's people.