«I never saw that you did painting need
And therefore to your fair no painting set».
Apparently having been reproached by the youth for withdrawing from competition against the rival poet, the poet argues that it is better not to write any poetry than to write falsely.
I never saw that you did painting need
Recalling the phrase “gross painting” from the previous sonnet, the poet responds to what must have been the young man’s accusation, “I never saw that you did painting need, / And therefore to your fair no painting set” — as opposed to the rival poet, whose “modern quill doth come too short, / Speaking of worth, what worth in you doth grow.”
Apparently proud of the superiority of his verse, the poet scornfully contrasts his verse with the strained and rhetorical verse of his rival, who ironically minimizes the youth’s beauty by his attempts to describe it: “For I impair not beauty, being mute, / When others would give life and bring a tomb.” Setting his faith in his plain, sincere style, nonetheless the poet knows that the rival poet remains in the youth’s favor: “There lives more life in one of your fair eyes / Than both your poets can in praise devise.” He seems resigned to the rival poet’s presence.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com