Jamieson, Fausset and Brown on Ecclesiastes 11:2

2. portion--of thy bread.

seven--the perfect number.

eight--even to more than seven; that is, "to many" (so "waters," Ec 11:1), nay, even to very many in need (Job 5:19; Mi 5:5).

evil--The day may be near, when you will need the help of those whom you have bound to you by kindnesses (Lu 16:9). The very argument which covetous men use against liberality (namely, that bad times may come), the wise man uses for it.