4 He who waits for the wind will not sow, and he who looks at the clouds will not reap. [note a]
5 As you do not know what is the way of the wind, just as things enclosed in the full womb; so will you not know GOD’s work, Who does everything. [note b]
6 In the morning, sow your seed, and in the evening, do not withhold your hand, for you know not which will succeed, this one or that one, or whether both of them will be equally good.
[note a] Do not look at, and do not value the work you do through distant and abstract manners (wind and clouds), do not rely on speculation because these are things for those who don’t believe in GOD. Those who have faith maintain it especially during adversity and through uncertainties and doubts, because aware that at the end it will never be abandoned by the CREATOR who always works for the good of His children.
[note b] GOD is the Creator of everything, He alone generates peace (the good) and creates evil (Isaiah 45, 5-7), both are necessary for the order of everythings. Even issues, events, which initially seem malicious, will always reveal itselves as the ultimate good, as GOD is only Love for Creation.
Check the Hebrew-English Interlinear Translation
Just as we do not know (verse 5) how the bones are shaped in the womb of the one who is pregnant, so we cannot know the work of GOD. We accept His work with the children He gives us, but we cannot trace the process of His work. We do not doubt the birth of the child that is conceived, although we do not know how it was formed;
So Solomon continues to invite the believer to proceed and persevere in work and doing good; without letting the doubts slip us no opportunity.
In the morning sow your seed (invest in some work or work) and in the evening do not hold your hand (do not hold back from doing other works), with the claim that you are tired.
We could also see a broader reference (to life): Youth is the morning, the little that you started with; and even on the evening of old age, do not give in to the common temptation to think and worry instead of acting, but work (work for good) to the last, because you do not know which work, this or that is accepted (as is) by GOD or maybe both will be good to your eyes.
Do not be tired of working and doing good, because in due time, at the time of GOD (and not ours as impatient men) the best moment will come and you will reap, (See Gal 6, 9) This is also applicable to Love spiritual, and to our pious efforts for the good of others; we continue to haunt them, because, even if we have worked in vain for a long time, we could finally see their success.