Augustine. Exposition on the Book of Psalms. Schaff, Philip (editor). New York: Christian Literature Publishing Co, 1886. Nicene and Post-Nicene Church Fathers: Series 1: Volume VIII. Re-published 2014, Catholic Way Publishing. Kindle electronic edition, ISBN-13: 978-1-78379-372-3.
Augustine ties Psalm 128 with a martyr named Felix, since the Psalm describes the "blessed" one. Verse one speaks of many who are blessed, but verse two shifts to a singular. Augustine takes this to refer to all Christians, who together function as one in Christ (Augustine Psalms, loc. 340757, par. 2).
In verse two, Augustine takes the text to actually say, "Thou shalt eat the labors of thy fruits" (Augustine Psalms, loc. 340767, par. 3). The statement, backward from what we would reasonably expect, draws notice. Augustine suggests that in Christ we are more interested in the work of God's kingdom than in what that work produces for us. The pleasurable reaping comes at some indeterminate time in the future. At that time we will take pleasure in the fruit.
Verse three speaks of "your wife." Here Augustine takes the Psalm to be about Christ, and his bride, the Church (Augustine Psalms, loc. 340777, par. 4). The bride is compared to a fruitful vineyard, though Augustine admits the Church contains many who are not bearing godly fruit. Yet there are always fruitful parts of the Church as well. The Psalm also refers to children. Augustine says that "in the Church, she who is the wife, is the children also" (Augustine Psalms, loc. 340782, par. 5). The rightful place of the children is around God's table. This is the blessing of verses four and five (Augustine Psalms, loc. 340797, par. 6). Augustine notes that God blesses other creatures, so we should expect him to bless his people as well. Augustine then urges care and dedication in raising children as Christians, so they can be a blessing to others as well (Augustine Psalms, loc. 340802, par. 7). This intergenerational life of service and blessing is, to Augustine, the greatest earthly blessing we have.