What's he saying?
"When in the chronicle of wasted time / I see descriptions of the fairest wights,"
[When, in history books, I read descriptions of the most beautiful men and women,]
"And beauty making beautiful old rhyme, / In praise of ladies dead and lovely knights,"
Their beauty shining through the old poetry, making it beautiful, written to praise those who lived long ago,
"Then, in the blazon of sweet beauty's best, / Of hand, of foot, of lip, of eye, of brow,"
In the record of their most beautiful parts, whether it be a hand, foot, lip, eye, or forehead,
"I see their antique pen would have expressed / Even such a beauty as you master now."
The poets of old would have risen to the challenge of representing even your beauty.
"So all their praises are but prophecies / Of this our time, all you prefiguring;"
All their praises were really about you, though you weren't alive yet;
"And for they looked but with divining eyes, / They had not skill enough your worth to sing:"
Since they only saw you as a premonition, they were unable to praise you adequately:
"For we, which now behold these present days, / Have eyes to wonder, but lack tongues to praise."
But I, who look upon you now, cannot write words beautiful enough to represent you.
Why is he saying it?
Sonnet 106 looks back in time, to a time recorded in the "chronicles" which the speaker reads. In contrast, many of Shakespeare's other sonnets to the fair lord have looked forward in time, to a point when the fair lord will either be dead or will have lost his youthful beauty, but will live on through the poet's work. Sonnet 17 is, in a way, a foil to Sonnet 106 by looking forward to a time when the poet's own work will be a "chronicle of wasted time," asking, "Who will believe my verse in time to come, / If it were fill'd with your most high deserts?"
Sonnet 106 seems to echo No. 50 in Samuel Daniel's Sonnets to Delia, published in 1594. The first four lines refer back to a time when the beauty of the "wights" Shakespeare refers to here was recorded by poets of old, but also points out that poets of the time are still looking back, praising the beauty of those long dead: "Let others sing of knights and paladins / In aged accents and untimely words, / Paint shadows in imaginary lines, / Which well the worth of their high wits records." The theme, however, has more in common with that of Shakespeare's Sonnet 17 and others that speak of the poet's hope for the future (specifically, that his verse will serve to represent the beloved's beauty for generations to come).
In this sonnet, the poet puts himself down, belittling his efforts to adequately praise the fair lord's beauty. This is a common theme throughout the sonnets, although it is ironic, since the sonnets themselves prove that the poet is, in fact, aptly representing his subject. The final couplet contrasts the speaker with the writers of the chronicle, pointing out that although he has an advantage over them by having the fair lord to look upon, rather than to just imagine as he might be in the future, still he and rival poets "lack tongues to praise."
The phrase "chronicle of wasted time" hearkens to the theme of Time as a destroyer, which "wastes," or lays waste to, the beautiful "wights" and their nations. This iteration of "wasted time" does not have the modern-day meaning of days spent in laziness, but rather is linked to its Latin derivative, "vasture," meaning destruction in warfare. The "chronicle" itself was a written historical record, often compiled by a monk. In writing his historical plays, Shakespeare is known to have relied on Holinshed's Chronicle History of England, which was published in 1577.
A Christian undertone runs through this sonnet, likening the fair lord to Jesus Christ, and perhaps his beauty to Christ's message. The bards of long ago were like prophets, writing about a beauty that was to come, but which they could not see yet, other than how it was reflected in the most beautiful men and women of their time. Line 9 states that, "all their praises are but prophecies" of the fair lord, who would come in the future (which is now the present-day, for the poet). The word "prophecies" in addition to the term "divining" in line 11 support the religious connection. "Divining" means seeing into the future, as fortune-tellers, and of course carries the connotation of something divine, from heaven.