In Genesis, a dove returned to Noah's Ark with a fresh olive leaf. Genesis 8:11 presents the leaf as evidence that the Flood waters had receded from the land.
The dove was sent after Noah had already released a raven. Noah released the dove more than once: it first returned without a sign, then came back with the olive leaf, and finally did not return when the ground had become suitable for life outside the ark.
The olive branch or leaf later became a widely recognized symbol of peace. That later symbolism grew from several traditions, including the Noah story and ancient Mediterranean imagery. Genesis itself uses the leaf primarily as a practical sign that vegetation was visible again.