Aeneid VI.868-886 (translations)
Tum pater Anchises lacrimis ingressus obortis:
"O nate, ingentem luctum ne quaere tuorum;
ostendent terris hunc tantum fata neque ultra
esse sinent. Nimium uobis Romana propago 870
uisa potens, superi, propria haec si dona fuissent.
quantos ille uirum magnam Mauortis ad urbem
campus aget gemitus! Vel quae, Tiberine, uidebis
funera, cum tumulum praeterlabere recentem!
Nec puer Iliaca quisquam de gente Latinos 875
in tantum spe tollet auos, nec Romula quondam
ullo se tantum tellus iactabit alumno.
Heu pietas, heu prisca fides inuictaque bello
dextera! Non illi se quisquam impune tulisset
obuius armato, seu cum pedes iret in hostem 880
seu spumantis equi foderet calcaribus armos.
Heu, miserande puer, si qua fata aspera rumpas,
tu Marcellus eris. manibus date lilia plenis,
purpureos spargam flores animamque nepotis
his saltem accumulem donis, et fungar inani 885
munere." Sic tota passim regione uagantur
aeris in campis latis atque omnia lustrant.

In this passage Aeneas' father Anchises eulogizes Marcellus at the end of the parade of famous Romans in the underworld:

Aeneid VI.868-886, translated by John Dryden

"Seek not to know," the ghost replied with tears,
"The sorrows of thy sons in future years.
This youth (the blissful vision of a day)
Shall just be shown on earth, and snatch'd away.
The gods too high had rais'd the Roman state,
Were but their gifts as permanent as great.
What groans of men shall fill the Martian field!
How fierce a blaze his flaming pile shall yield!
What fun'ral pomp shall floating Tiber see,
When, rising from his bed, he views the sad solemnity!
No youth shall equal hopes of glory give,
No youth afford so great a cause to grieve;
The Trojan honor, and the Roman boast,
Admir'd when living, and ador'd when lost!
Mirror of ancient faith in early youth!
Undaunted worth, inviolable truth!
No foe, unpunish'd, in the fighting field
Shall dare thee, foot to foot, with sword and shield;
Much less in arms oppose thy matchless force,
When thy sharp spurs shall urge thy foaming horse.
Ah! couldst thou break thro' fate's severe decree,
A new Marcellus shall arise in thee!
Full canisters of fragrant lilies bring,
Mix'd with the purple roses of the spring;
Let me with fun'ral flow'rs his body strow;
This gift which parents to their children owe,
This unavailing gift, at least, I may bestow!"
Thus having said, he led the hero round
The confines of the blest Elysian ground; 

Aeneid VI.868-886, translated by C. Day Lewis

"What lamentations of men shall the Campus Martius echo
To Mars' great city! O Tiber, what obsequies you shall see
One day as you glide past the new-built mausoleum! 
No lad of the Trojan line shall with such hopeful promise
Exalt his Latin forebears, nor shall the land of Romulus
Ever again be so proud of one she has given birth to.
Alas for the sense of duty, the old-time honour! Alas for
The hand unvanquished in war!  Him would no foe have met
In battle and not rued it, whether he charged on foot
Or drove his lathering steed with spurs against the enemy.
Alas, poor youth! If only you could escape your harsh fate!
Marcellus you shall be.  Give me armfuls of lilies
That I may scatter their shining blooms and shower these gifts
At least upon the dear soul, all to no purpose though
Such kindness be."