Gregory the Dialogist

Hence those who had preceded in labor also say, murmuring: These last worked one hour, and you have made them equal to us who have borne the burden of the day and the heat? For those have borne the burden of the day and the heat whom it befell from the beginning of the world, because they happened to live here for a long time, to endure also longer temptations of the flesh. For to bear the burden of the day and the heat is for each one to be wearied by the heat of his flesh through the times of a longer life.

Forty Gospel Homilies, Homily 19 ↗

Hilary of Poitiers

And this murmur of the labourers corresponds with the frowardness of this nation, which even in the time of Moses were stiff-necked.

Catena Aurea by Aquinas ↗

Thomas Aquinas

And having received it, they murmured against the master of the house, saying: these last have worked but one hour, etc. Above, the remuneration was set forth; here, the murmuring of some is set forth. But here there is a twofold question, because he says that those who received each their denarius murmured. By the denarius is understood eternal life. Is it to be believed that anyone would murmur after receiving his reward? …

Commentary on Matthew ↗