«Say that thou didst forsake me for some fault,
And I will comment upon that offence».
Continuing where the previous sonnet left off, this sonnet reveals an undertone of apprehension in the poet’s references to the young man. Whatever the slanderous accusation the youth will make against him, the poet promises to prove the youth justified.
Say that thou didst forsake me for some fault,
Loving the young man and knowing that the young man wishes to forsake him will be enough to impel the poet to act against his own best interests.
So far the friendship is not completely dead. Throughout the sonnet, the poet uses the future tense because for all his insecurity and doubts, the dissolution of the relationship is not yet final. Hoping that such an end never occurs, the poet promises to correct any fault in himself that the youth might find. He consistently wars against himself for the youth’s sake: “For thee, against myself I’ll vow debate, / For I must ne’er love him whom thou dost hate.”
In other words, because the poet views himself and the youth as one indivisible person, if the youth should begin to hate the poet, then the poet would essentially begin to hate himself since he and the youth are the same person — at least in the poet’s mind, but certainly not in the youth’s.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com