A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
ecc 11:1(Ecc 11:1-10)
Ecc 11:2 shows that charity is here inculcated.
bread--bread corn. As in the Lord's prayer, all things needful for the body and soul. Solomon reverts to the sentiment (Ecc 9:10).
waters--image from the custom of sowing seed by casting it from boats into the overflowing waters of the Nile, or in any marshy ground. When the waters receded, the grain in the alluvial soil sprang up (Isa 32:20). "Waters" express multitudes, so Ecc 11:2; Rev 17:15; also the seemingly hopeless character of the recipients of the charity; but it shall prove at last to have been not thrown away (Isa 49:4).
ecc 11:2portion--of thy bread.
seven--the perfect number.
eight--even to more than seven; that is, "to many" (so "waters," Ecc 11:1), nay, even to very many in need (Job 5:19; Mic 5:5).
evil--The day may be near, when you will need the help of those whom you have bound to you by kindnesses (Luk 16:9). The very argument which covetous men use against liberality (namely, that bad times may come), the wise man uses for it.
ecc 11:3clouds--answering to "evil" (Ecc 11:2), meaning, When the times of evil are fully ripe, evil must come; and speculations about it beforehand, so as to prevent one sowing seed of liberality, are vain (Ecc 11:4).
tree--Once the storm uproots it, it lies either northward or southward, according as it fell. So man's character is unchangeable, whether for hell or heaven, once that death overtakes him (Rev 22:11, Rev 22:14-15). Now is his time for liberality, before the evil days come (Ecc 12:1).
ecc 11:4Therefore sow thy charity in faith, without hesitancy or speculation as to results, because they may not seem promising (Ecc 9:10). So in Ecc 11:1, man is told to "cast his bread corn" on the seemingly unpromising "waters" (Psa 126:5-6). The farmer would get on badly, who, instead of sowing and reaping, spent his time in watching the wind and clouds.
ecc 11:5spirit--How the soul animates the body! Thus the transition to the formation of the body "in the womb" is more natural, than if with MAURER we translate it "wind" (Ecc 1:6; Joh 3:8).
bones . . . grow-- (Job 10:8-9; Psa 139:15-16).
knowest not the works of God-- (Ecc 3:11; Ecc 8:17; Ecc 9:12).
ecc 11:6morning . . . evening--early and late; when young and when old; in sunshine and under clouds.
seed--of godly works (Hos 10:12; Co2 9:10; Gal 6:7).
prosper-- (Isa 55:10-11).
both . . . alike--Both the unpromising and the promising sowing may bear good fruit in others; certainly they shall to the faithful sower.
ecc 11:7light--of life (Ecc 7:11; Psa 49:19). Life is enjoyable, especially to the godly.
ecc 11:8But while man thankfully enjoys life, "let him remember" it will not last for ever. The "many days of darkness," that is, the unseen world (Job 10:21-22; Psa 88:12), also days of "evil" in this world (Ecc 11:2), are coming; therefore sow the good seed while life and good days last, which are not too long for accomplishing life's duties.
All that cometh--that is, All that followeth in the evil and dark days is vain, as far as work for God is concerned (Ecc 9:10).
ecc 11:9Rejoice--not advice, but warning. So Kg1 22:15, is irony; if thou dost rejoice (carnally, Ecc 2:2; Ecc 7:2, not moderately, as in Ecc 5:18), &c., then "know that . . . God will bring thee into judgment" (Ecc 3:17; Ecc 12:14).
youth . . . youth--distinct Hebrew words, adolescence or boyhood (before Ecc 11:10), and full-grown youth. It marks the gradual progress in self-indulgence, to which the young especially are prone; they see the roses, but do not discover the thorns, until pierced by them. Religion will cost self-denial, but the want of it infinitely more (Luk 14:28).
ecc 11:10sorrow--that is, the lusts that end in "sorrow," opposed to "rejoice," and "heart cheer thee" (Ecc 11:9), Margin, "anger," that is, all "ways of thine heart"; "remove," &c., is thus opposed to "walk in," &c. (Ecc 11:9).
flesh--the bodily organ by which the sensual thoughts of the "heart" are embodied in acts.
childhood--rather, "boyhood"; the same Hebrew word as the first, "youth" in Ecc 11:9. A motive for self-restraint; the time is coming when the vigor of youth on which thou reliest, will seem vain, except in so far as it has been given to God (Ecc 12:1).
youth--literally, the dawn of thy days.