Rather, What has been - what was before, and what shall be has been before. The word "is" in our the King James Version is erroneously printed in Roman letters: it does not exist in the Hebrew (it should have been italicized); and the word there translated "now" is the same which is translated as "already."
Requireth - i. e., requireth for judgment, as the word specially means in 2-Samuel 4:11; Ezekiel 3:18...It is obvious from the context of the last clause of Ecclesiastes 3:14, and Ecclesiastes 3:16-17, that this is the meaning here.
Past - literally, "put to flight."
The meaning of the verse is that there is a connection between events - past, present and future - and that this connection exists in the justice of God who controls all.

That which hath been is now - God governs the world now, as he has governed it from the beginning; and the revolutions and operations of nature are the same now, that they have been from the beginning. What we see now, is the same as has been seen by those before us.
And God requireth that which is past - i.e., That it may return again in its proper order. The heavens themselves, taking in their great revolutions, show the same phenomena. Even comets are supposed to have their revolutions, though some of them are hundreds of years in going round their orbits.
But in the economy of grace, does not God require that which is past? Whatever blessing or influence God gives to the soul of man, he intends shall remain and increase; and it will, if man be faithful. Reader, canst thou produce all the secret inspirations of his Spirit, all the drawings of his love, his pardoning mercy, his sanctifying grace, the heavenly-mindedness produced in thee, thy holy zeal, thy spirit of prayer, thy tender conscience, the witness of the Spirit, which thou didst once receive and enjoy? Where are they? God requireth that which is past.

That which hath been is now; and that which is to be hath already been; and God (f) requireth that which is past.
(f) God only causes what which is past, to return.

That which hath seen is now; and that which is to be hath already been,.... That which has been from the beginning now is; that which cometh, and what shall be in the end of days, has been already, as the Targum. Jarchi interprets this of God and his attributes, which are always the same; he is the "I am that I am", Exodus 3:14; the immutable and eternal Jehovah, which is, and was, and is to come, invariably the same. Or rather it designs his decrees and purposes; what has been decreed in his eternal mind is now accomplished; and what is future has been already in his decrees; nor does anything come to pass but what he has appointed. So it is interpreted, in an ancient tract (p) of the Jews, of
"what was before it came into the world, so that there is nothing new under the sun; now it is obliged to come into this world, as it is said, "before I formed thee in the belly, I knew thee", Jeremiah 1:5.''
This will also hold true of natural things, and of the identity of them; of some individuals, as the sun, moon, and stars, which are as they always were, and will be; the sun rises and sets as it used to do; and the moon increases and decreases, as it always has done; and the stars keep the same station or course, and so they ever will, as they have: the same seasons are now in their turn as heretofore, and such as will be have been already; as summer, winter, spring, autumn, seedtime, harvest, cold, heat, night, and day: the same kinds and species of creatures, that have been, are; and what will be have been already; so that there is no new thing under the sun; the same thing is here expressed as in Ecclesiastes 1:9;
and God requireth that which is past; his decrees and purposes to be fulfilled, which are past in his mind; the same seasons to return which have been; and the same kinds and species of creatures to exist which have already. The words may be rendered, "and God seeketh that which is pursued", or "persecuted" (q): and accordingly the whole will bear a different sense; and the preacher may be thought to have entered upon a new subject, which he continues in some following verses, the abuse of power and authority: and the meaning then is, the same acts of injustice, violence, and persecution, have been done formerly as now, and now as formerly; and what hereafter of this kind may be, will be no other than what has been; from the beginning persecution was; Cain hated and slew his brother, because of his superior goodness; and so it always has been, is, and will be, that such who are after the flesh persecute those who are after the spirit; but God will make inquisition for blood, and require it at the hands of those that shed it; he will seek out the persecuted, and vindicate him, and, avenge his persecutor. This way the Midrash, Jarchi, and Alshech, and the Septuagint version, render the words; and so the Syriac version, "God seeketh him that is afflicted, who is driven away"; and to this agrees the Targum,
"and in the great day which shall be, the Lord will require the mean and poor man of the hands of the wicked that persecute him.''
And what follows seems to confirm this sense.
(p) Tikkune Zohar Correct. 69. fol. 104. 2. (q) "Deus quaerit propulsum, seu quod persecutionem veluti passum est", Gejerus, Schmidt.

Resumption of Ecclesiastes 1:9. Whatever changes there be, the succession of events is ordered by God's "everlasting" laws (Ecclesiastes 3:14), and returns in a fixed cycle.
requireth that . . . past--After many changes, God's law requires the return of the same cycle of events, as in the past, literally, "that which is driven on." The Septuagint and Syriac translate: "God requireth (that is, avengeth) the persecuted man"; a transition to Ecclesiastes 3:16-17. The parallel clauses of the verse support English Version.

"That which is now hath been long ago; and that which will be hath already been: God seeketh after that which was crowded out." The words: "hath been long ago" (הוּא כּבר), are used of that which the present represents as something that hath been, as the fruit of a development; the words: "hath already been" (היה כּבר), are used of the future (ל אשׁר, τὸ μέλλον, vid., Gesen. 132. 1), as denying to it the right of being regarded as something new. The government of God is not to be changed, and does not change; His creative as well as His moral ordering of the world produces with the same laws the same phenomena (the ו corresponds to this line of thought here, as at Ecclesiastes 3:14) - God seeks את־ן (cf. Ecclesiastes 7:7; Ewald, 277d). Hengstenberg renders: God seeks the persecuted (lxx, Symm., Targ., Syr.), i.e., visits them with consolation and comfort. Nirdaph here denotes that which is followed, hunted, pressed, by which we may think of that which is already driven into the past; that God seeks, seeks it purposely, and brings it back again into the present; for His government remains always, and brings thus always up again that which hath been. Thus Jerome: Deut instaurat quod abiit; the Venet.: ὃ τηεὸς ζητήσει τὸ ἀπεληλαμένον; and thus Geier, among the post-Reform. interpreters: praestat ut quae propulsa sunt ac praeterierunt iterum innoventur ac redeant; and this is now the prevailing exposition, after Knobel, Ewald, and Hitzig. The thought is the same as if we were to translate: God seeks after the analogue. In the Arab., one word in relation to another is called muradif, if it is cogn. to it; and mutaradifat is the technical expression for a synonym. In Hebrews. the expression used is שׁמות נרדּפים, they who are followed the one by another, - one of which, as it were, treads on the heels of another. But this designation is mediated through the Arab. In evidence of the contrary, ancient examples are wanting.

Hath been - Things past, present, and to come, are all ordered by one constant counsel, in all parts and ages of the world. There is a continual return of the same motions of the heavenly bodies, of the same seasons of the year, and a constant succession of new generations of men and beasts, but all of the same quality.