Building the Ark
God instructed Noah to build an ark to exact dimensions, sealed with pitch, and to bring aboard his wife, his three sons and their wives — eight in all — along with clean and unclean living things of the earth, "seven pairs" or "a pair" of each. Rain fell forty days and nights, the flood covered the whole earth, and every living thing outside the ark perished.
The Dove Returns With an Olive Leaf
As the flood receded, Noah sent out a raven and then a dove to scout the waters; when the dove returned a third time, it carried in its beak a freshly plucked olive leaf, and Noah knew the waters had abated. The "olive branch" became a symbol of peace and hope ever after — the olive-branch motif on the United Nations flag comes from exactly this.