Avad means to work, serve, labor, or worship. It appears about 290 times in the OT. The noun form is eved (servant/slave, H5650). The range of avad spans physical labor (Adam in the garden, Genesis 2:15), covenantal service to a king, and the highest form of worship and devotion to God.
In Hebrew thought, there is no sharp distinction between "serving" and "worshiping" God — both are avad. The verb that describes tilling the soil is the same verb used for priestly service at the altar and for the nation's whole-life consecration to YHWH.
Genesis 2:15 says God placed Adam in the garden "to work it and take care of it" — the verbs are avad (work/serve) and shamar (keep/guard). Human vocation from creation is priestly: tending God's world as an act of worship.
The central demand of the Exodus is not just liberation but reorientation of avad. Israel had been serving Pharaoh (avad); God rescues them so they may serve Him (avad). Moses's recurring refrain: "Let my people go, that they may serve me (avad)" (Exodus 7:16).
The Eved YHWH — Servant of the LORD — passages in Isaiah (42:1–9; 49:1–6; 50:4–9; 52:13–53:12) describe the Messiah as the ultimate embodiment of avad. He serves perfectly where Israel failed. The church, as Christ's body, inherits this servant identity.