5 In this context the shortened prefix form does not function as a preterite, but indicates what is typical of the world.
6 The Hebrew term דַּכָּא (daka’) carries the basic sense of “crushed.” Elsewhere it refers to those who are “crushed” in spirit or contrite of heart (see Ps 34:18; Isa 57:15). If one understands this nuance here, then v. 3 is observing that God leads mankind to repentance (the term שׁוּב, shuv, “return,” which appears twice in this verse, is sometimes used of repentance.) However, the following context laments mankind’s mortality and the brevity of life, so it is doubtful if v. 3 should be understood so positively. It is more likely that דַּכָּא here refers to “crushed matter,” that is, the dust that fills the grave (see I דַּכָּא; 194 דַּכָּא). In this case one may hear an echo of Gen 3:19.
7 Or “for.”
8 The divisions of the nighttime. The ancient Israelites divided the night into distinct periods, or “watches.”
9 Heb “you bring them to an end [with] sleep.” The Hebrew verb זָרַם (zaram) has traditionally been taken to mean “flood” or “overwhelm” (note the Polel form of a root זרם in Ps 77:17, where the verb is used of the clouds pouring down rain). However, the verb form here is Qal, not Polel, and is better understood as a homonym meaning “to make an end [of life].” The term שֵׁנָה (shenah, “sleep”) can be taken as an adverbial accusative; it is a euphemism here for death (see Ps 76:5–6).
10 Or “flourishes.” The verb is used of a crown shining in Ps 132:18. Perhaps here in Ps 90:6 it refers to the glistening of the grass in the morning dew.
11 The Polel form of this verb occurs only here. Perhaps the form should be emended to a Qal (which necessitates eliminating the final lamed [ל] as dittographic). See Ps 37:2.

In other versions

ESVEnglish Standard Version

You return man to dust

and say, “Return, O children of man!”

For a thousand years in your sight

are but as yesterday when it is past,

or as a watch in the night.

You sweep them away as with a flood; they are like a dream,

like grass that is renewed in the morning:

in the morning it flourishes and is renewed;

in the evening it fades and withers.

NIVNew International Version (2011)

You turn people back to dust,

saying, “Return to dust, you mortals.”

A thousand years in your sight

are like a day that has just gone by,

or like a watch in the night.

Yet you sweep people away in the sleep of death—

they are like the new grass of the morning:

In the morning it springs up new,

but by evening it is dry and withered.

CSBChristian Standard Bible

You return mankind to the dust,

saying, “Return, descendants of Adam.”

For in your sight a thousand years

are like yesterday that passes by,

like a few hours of the night.

You end their lives; they sleep.

They are like grass that grows in the morning—

in the morning it sprouts and grows;

by evening it withers and dries up.

NLTNew Living Translation

You turn people back to dust, saying,

“Return to dust, you mortals!”

For you, a thousand years are as a passing day,

as brief as a few night hours.

You sweep people away like dreams that disappear.

They are like grass that springs up in the morning.

In the morning it blooms and flourishes,

but by evening it is dry and withered.

LEBThe Lexham English Bible

You return man to the dust,

saying, “Return, O sons of man.”

For a thousand years in your eyes

are like yesterday when it passes,

or like a watch in the night.

You sweep them away like a flood.

They fall asleep.

In the morning they are like grass that sprouts anew.

In the morning it blossoms and sprouts anew;

by evening it withers and dries up.

KJV 1900King James Version

Thou turnest man to destruction;

And sayest, Return, ye children of men.

For a thousand years in thy sight

Are but as yesterday when it is past,

And as a watch in the night.

Thou carriest them away as with a flood; they are as a sleep:

In the morning they are like grass which groweth up.

In the morning it flourisheth, and groweth up;

In the evening it is cut down, and withereth.

Public Domain