=18. VESTRA= = 'of you [plural] at Rome'.
=18. CARMEN IN ORA DEDI.= 'I sent a poem for you to recite from and speak of'. _Dare_ meaning 'send' is usually restricted to use with _litteras_ (_OLD do_ 10; compare Cic _Att_ II i 12 & IX viiB 1, Livy XXVII 16 13).
For _in ora_, compare Catullus XL 5 'an ut peruenias _in ora_ uulgi [_sc_ hoc facis]?', Hor _Ep_ I iii 9 ' ... Titius, Romana breui uenturus _in ora_', Prop III ix 32 (to Maecenas) 'et uenies tu quoque _in ora_ uirum', _Tr_ V vii 29-30 'non tamen ingratum est quodcumque obliuia nostri / impedit et profugi nomen _in ora_ refert', and Livy II 36 3. The only instance I have found of the expression being used of a thing rather than a person other than this passage is also from Ovid: 'illud opus ... nunc incorrectum populi peruenit _in ora_, / in populi quicquam si tamen ore mei est' (_Tr_ III xiv 21-24). Neither passage would have seemed strange to the Romans, given the close identification between poet and work: compare Ennius' famous 'uolito uiuo' per ora uirum' and _Met_ XV 878 'ore legar populi'.
=19. QVAE PIETAS.= 'This demonstration of loyalty'.
=20. SACRAE ... DOMVS.= Augustus' house called 'magni ... Iouis ... domum' at _Tr_ III i 38; compare as well _EP_ III i 135 'domus Augusti, Capitoli more colenda'.
=20. MITIOR IRA.= Compare _EP_ III iii 83 'pone metus igitur: _mitescet_ Caesaris _ira_'.
=21. LIQVIDO POSSVM IVRARE.= 'I can swear unambiguously'. The only other instance of this sense in verse apparently III iii 49-50 'scis tamen et _liquido_ iuratus dicere possis / non me legitimos sollicitasse toros'. From prose compare Cic _II Verr_ IV 124 'confirmare hoc _liquido_, iudices, possum, ualuas magnificentiores ... nullas umquam ullo in templo fuisse', _II Verr_ III 136, _Fam_ XI 27 7 'alia sunt quae _liquido_ negare soleam', and Sen _Ben_ VII 9 5.
=22. NON DVBIA ... NOTA.= The phrase logically belongs with the preceding line: on the firm evidence of Brutus' past behaviour (described in 23-42), Ovid can confidently state that Brutus prays for his restoration. _Non dubia_ by litotes for _certa_ (for which see _Her_ XX 207 'te ... nimium miror, _nota certa_ furoris'); _nota_ 'tangible sign, evidence' similarly used at _Met_ I 761 (_generis_). FIDE (_LTM2ulF2ul_) is an obvious gloss for _nota_.