Boast not thyself of to morrow; for thou knowest not what a day may bring forth.
Boast not thyself of to-morrow (of what thou wilt do tomorrow); for thou knowest not what a day may bring forth - what event will happen on the morrow to prevent thine intention. Events are called by the Hebrews sons of time. Time brings them forth, as the pregnant woman knows not whether her child will be male or female, living or dead.