Against that time, if ever that time come,
When I shall see thee frown on my defects,
When as thy love hath cast his utmost sum,
Called to that audit by advis'd respects;
Against that time when thou shalt strangely pass,
And scarcely greet me with that sun, thine eye,
When love, converted from the thing it was,
Shall reasons find of settled gravity;
Against that time do I ensconce me here,
Within the knowledge of mine own desert,
And this my hand, against my self uprear,
To guard the lawful reasons on thy part:
   To leave poor me thou hast the strength of laws,
   Since why to love I can allege no cause.

The poet gazes into the future and foresees a time when love will have perished, and the beloved youth will pass him by with averted eyes, scarcely looking upon the one he so much cherished in the past. In advance the poet forgives him, and declares that he himself will take the witness stand against himself. Love has no rationality, and the poet himself cannot find reasons as to why the youth should love him, since beauty, worth, wealth and wit belong to the youth, not to the poet. Therefore he forgives him his eventual desertion in advance, and justifies it in legal and formal terms.

The number 49 was regarded by the Elizabethans as an important, even critical number, being the seventh multiple of seven. Seventh sons were looked upon with special awe, the seventh son of a seventh son even more so. They were thought to have special healing powers. A quack in James I time was prosecuted for claiming to cure 'the evil' by the Touch, but it was discovered that his father had had only six sons. (Shakespeare’s England, Oxford 1916, I.427.) Elizabeth's survival past the grand climacteric, the 63rd year of her life, was thought to be almost miraculous.

One therefore expects that this sonnet would have some special significance, given that Shakespeare seems to have taken great care over the numerical arrangement of the sequence. Nos. 12 and 60 both relate to clocks, and the total number of sonnets dedicated to the youth is 126, exactly double the grand climacteric number (63). In fact the most striking fact is that this sonnet, 49, and 63, both begin with the same words, and both look to the future, and to the farewell sonnet No 126.

Against that time, if ever that time come, 49.
Against my love shall be as I am now 63.
Called to that audit by advis'd respects; 49.
Her audit though delayed answered must be, 126.

It is as though the poet wishes to summarise and encapsulate the history of his love in these few sonnets placed at a critical juncture in the series. He is submitting to an audit of his love and doing so before the final event of death and separation, the end of all things mortal, however eternal they might have seemed for the moment, or in the glorious bravado of some of the eternising sonnets of the series.

The 1609 Quarto Version

AGainſt that time ( if ever that time come )
When I ſhall ſee thee frowne on my defects,
When as thy loue hath caſt his vtmoſt ſumme,
Cauld to that audite by aduiſ'd reſpects,
Againſt that time when thou ſhalt ſtrangely paſſe,
And ſcarcely greete me with that ſunne thine eye,
When loue conuerted from the thing it was
Shall reaſons finde of ſetled grauitie.
Againſt that time do I inſconce me here
Within the knowledge of mine owne deſart,
And this my hand,againſt my ſelfe vpreare,
To guard the lawfull reaſons on thy part,
   To leaue poore me,thou haſt the ſtrength of lawes,
   Since why to loue,I can alledge no cauſe.


1. Against that time, if ever that time come,
Against that time = in preparation for that time.
if ever that time come - he leaves open the possibility that the youth might remain forever faithful.
2. When I shall see thee frown on my defects,
defects = failings (physical, spiritual, social, moral); taints; inadequacies. It is worth noting that a frown from the beloved beauty (usually a woman) was often the source of great agony to the lover. He frequently thought that it would be enough to kill him. For example Daniel's 19th sonnet to Delia:
If Beautie thus be clouded with a frowne,
That pittie shines no comfort to my blis:
And vapors of disdaine so ouergrowne,
That my liues light thus wholy darkned is.
Why should I more molest the world with cryes?

There is doubtless an element of parody in this lover's language.
3. When as thy love hath cast his utmost sum,
When as = At the time when, when the time comes that;
hath cast his utmost sum = has done its final summation of profit and loss; finally attempts to balance the account on both sides. utmost suggests an effort to extend the limit of his love beyond its natural termination date. The imagery is of accounting, and hard nosed business realism, confirmed by audit in the next line. There is therefore an implied criticism of the youth's mercenary and calculating love, as opposed to that of the poet, which is boundless and free. The word cast also has the association of the biblical casting pearls before swine, implying here that the poet is not worthy of so great a love (he is the swine, the youth the pearl), or exactly the opposite, the youth being unworthy.
4. Called to that audit by advis'd respects;




 audit = an examination of accounts. In 4 and 126, in Q, the word is italicised and capitalised, in the latter case being spelt Audite, as here. This spelling emphasises the root meaning of the word, as a summons to a hearing in which the accounts were presented and examined by officials. advised respects = considerations of one's position in society. The word advised suggests the listening to advice given by others about the danger of friendship with unsuitable persons, for example, the damage to one's social standing, etc. etc. Shakespeare uses the phrase in John.IV.2.

 It is the curse of kings to be attended
By slaves that take their humours for a warrant
To break within the bloody house of life,
And on the winking of authority
To understand a law; to know the meaning
Of dangerous majesty, when perchance it frowns
More upon humour than advised respect.

5. Against that time when thou shalt strangely pass,
strangely = as a stranger; awkwardly.
pass = walk past, pass by.
6. And scarcely greet me with that sun, thine eye,
that sun, thine eye - this recalls the imagery of 7, 18, 33. in which the sun is an eye which looks upon the world, or is associated with eyes in some way. In fact, contrary to first impressions, the word 'sun' is not used very often in the sonnets, only eight times (including one plural), whereas 'eye' occurs much more frequently. (eye = 28, eyes = 36). The idea conveyed here is that of the majesty of the sun which the eye of the beloved recalls. It gilds all objects upon which it looks.
7. When love, converted from the thing it was,
converted = turned away. The basic meaning is to turn or revolve, from the Latin convertere. Used thus here and in Sonn.7:
The eyes, 'fore duteous, now converted are
From his low tract and look another way:

But the figurative meaning of to cause to change a belief or religion is also present, and was used elsewhere by Shakespeare. Cf. MV:
In converting Jews to Christians, you raise the price of pork.
MV. III..5.37.
the thing it was
- as HV points out, it is as if he cannot find adequate words to express what the love of the youth was towards him.
8. Shall reasons find of settled gravity;

reasons = reasons to justify desertion;
settled gravity = well-established, or staid sobriety. The basic meaning of gravity derives from the term gravitas applied to men of high standing in ancient Rome, the patricians (or optimates). It denoted seriousness of purpose and behaviour. The nearest modern equivalents are sobriety, dignity,  decorum, seriousness. Cf.
I never heard a man of his place, gravity, and learning, so wide of his own respect.

9. Against that time do I ensconce me here,
ensconce = secure myself with fortifications; figuratively - set myself up in a position ready for defence. A sconce was a minor fortification or earthwork. The poet here is however not planning to defend himself, but to defend the youth against the alleged crime of desertion.
Note the repetition of Against that time. It has been used like the tolling of a bell as the opening phrase for each of the three quatrains.
10. Within the knowledge of mine own desert,
His knowledge of his own (un)worthiness will be the basis of his defence of the youth.
11. And this my hand, against my self uprear,
As in a military encounter; or in taking an oath in the witness box. uprear = lift up.
this my hand could also apply to hand-writing, hence to the poem itself.
12. To guard the lawful reasons on thy part:
To guard - A continuation of the military metaphor. The meaning here seems to be to offer as a defence, to guard you with lawful reasons etc.
on thy part
= which are your rightful claim.
13. To leave poor me thou hast the strength of laws,
poor me - a typical belittlement of his own worth, which as elsewhere has a double edged meaning. The lover is poor because he is potentially in so much danger of being abandoned by the loved one. The phraseology also suggests the behaviour of the magnate who insists on interpreting the letter of the law and stifles humanity in the process, one who would squeeze the last penny from a widow as payment of a debt. Compare Shylock's insistence on the law in MV.
14. Since why to love I can allege no cause.

I can allege no cause - the formula is a legal or ecclesiastical one, as in The Book of Common Prayer 1549. Matrimony: ...Yf no impedimente bee alleged. OED also gives 1513–14 Act 5 Hen. VIII, c. 1 If the same persons...obiecte or allege any cause why he shall not soo doo. (Under object). See also 150 line 10.