Phaedrus, Fables 4.3

fame coacta vulpes alta in vinea
uvam adpetebat, summis saliens viribus.
quam tangere ut non potuit, discedens ait:
‘nondum matura es; nolo acerbam sumere.’
qui facere quae non possunt, verbis elevant,
adscribere hoc debebunt exemplum sibi.

A fox, driven on by hunger, made his attack on a bunch of grapes on a tall vine, jumping up with all his strength. When he wasn’t able to touch it, he walked away saying, ‘You’re not ripe yet; I don’t want to eat a sour bunch.’ Those people who use words to make light of what they’re incapable of doing will need to take this as their model.

Phaedrus, Fables 5.5.1-3

pravo favore labi mortales solent
et, pro iudicio dum stant erroris sui,
ad paenitendum rebus manifestis agi.

Mortals tend to slip up as a result of improper partiality; and while they stand to defend their error they tend to be driven to be repentant by the plain facts.

Phaedrus, Fables 3.11

eunuchus litigabat cum quodam improbo,
qui super obscena dicta et petulans iurgium
damnum insectatus est amissi corporis.
‘en’ ait ‘hoc unum est cur laborem validius,
integritatis testes quia desunt mihi.
sed quid Fortunae, stulte, delictum arguis?
id demum est homini turpe quod meruit pati.’

A eunuch was suing an impudent man who, as well as obscene remarks and insolent abuse, cast insults at him because of the loss his body had suffered. ‘Hey!’ said the eunuch, ‘The only reason why I’m labouring rather hard is that I lack witnesses to my integrity. But why, you idiot, do you reprove me for the fault of Fortune? It is only shameful for a man if his suffering is well deserved.’

The point of this tale is that there’s a none-too-subtle pun on ‘integritatis testes’ – which can also mean ‘the testicles that would make me complete’.