It was the time when sleep first comes to weary mortals,
creeping over us, the sweetest gift of gods.

[Tempus erat quo prima quies mortalibus aegris
incipit et dono divum gratissima serpit.]

Virgil (70-19 BC) Roman poet [b. Publius Vergilius Maro; also Vergil]

The Aeneid [Ænē̆is], Book 2, l. 268ff (2.268-269) (29-19 BC) [tr. Bartsch (2021)]
    (Source)

(Source (Latin)). Alternate translations:

It was the time, first sleep the weary soule
Possest, and heavens best gift on mortalls stole.
[tr. Ogilby (1649)]

'T was in the dead of night, when sleep repairs
Our bodies worn with toils, our minds with cares.
[tr. Dryden (1697)]

It was the time when the first sleep invades languid mortals, and steals upon them, by the gift of the gods, most sweet.
[tr. Davidson/Buckley (1854)]

It was the hour when Heaven gives rest
To weary man, the first and best.
[tr. Conington (1866)]

It was the hour when first their sleep begins
For wretched mortals, and most gratefully
Creeps over them, by bounty of the gods.
[tr. Cranch (1872), l. 271ff]

It was the time when by the gift of God rest comes stealing first and sweetest on unhappy men.
[tr. Mackail (1885)]

It was the time when that first peace of sick men hath begun,
By very gift of God o'er all in sweetest wise to creep.
[tr. Morris (1900)]

'Twas now the time, when on tired mortals crept
First slumber, sweetest that celestials pour.
[tr. Taylor (1907), st. 36, l. 316ff]

That hour it was when heaven's first gift of sleep
on weary hearts of men most sweetly steals.
[tr. Williams (1910)]

It was the hour when for weary mortals their first rest begins, and by grace of the gods steals over them most sweet.
[tr. Fairclough (1916)]

It was the time when the first sleep begins
For weary mortals, heaven’s most welcome gift.
[tr. Humphries (1951)]

It was the hour when worn-out men begin to get
Some rest, and by god's grace genial sleep steals over them.
[tr. Day Lewis (1952)]

It was the hour when for troubled mortals
rest -- sweetest gift of gods that glides to men --
has just begun.
[tr. Mandelbaum (1971), l. 371ff]

That time of night it was when the first sleep,
Gift of the gods, begins for ill mankind,
Arriving gradually, delicious rest.
[tr. Fitzgerald (1981), l. 360ff]

It was the time when rest, the most grateful gift of the gods, was first beginning to creep over suffering mortals.
[tr. West (1990)]

It was the hour when first sleep begins for weary mortals,
and steals over them as the sweetest gift of the gods.
[tr. Kline (2002)]

At that late hour, when sleep begins to drift
Upon fretful humanity as grace from the gods ....
[tr. Lombardo (2005), l. 319ff]

This was the hour when rest, that gift of the gods
most heaven-sent, first comes to beleaguered mortals,
creeping over us now.
[tr. Fagles (2006), l. 339ff]