
The Olive Tree appears to have been native to Palestine and has been cultivated since ancient times. Therefore, Olive Oil was in common use throughout its history and was used as a sacred sign in Anointing. Anointing is the act of establishing a Person, Place, or Thing in Total dedication to GOD.
In Genesis we read that Jacob on his way to Haran, stopped at a certain shrine for the night and used a stone to lay his head on. In a dream he experienced God speaking to him and when he woke he cried out,
"How awesome is this shrine!
This is nothing else but the abode of God ,
and that is the gateway to heaven."
(Gn 28:17)
In memory of this event, Jacob took the stone which he had used as a pillow, set is up and poured oil on top of it, thus indicating that this spot was sacred or dedicated to God.
In Exodus the LORD told Moses to make a perfumed Sacred Ointment by mixing myrrh, cinnamon, cane, cassia-all with olive oil. With this oil Moses was to anoint the Meeting Tent, Ark of the Commandments, the Table and all its articles, the Lampstand, Altars of Incense and holocaust. (Ex 30:20-28) The anointing would make the objects sacred to be used only in God's service. Also "Aaron and his sons you shall also anoint and consecrate as my priests." (Ex30:30) The oil used in anointing was itself sacred so that "Whoever prepares a perfume like this, or whoever puts any of this on a layman, shall be cut off from his kinsmen". (Ex30:33)

Here we see Samuel anointing young David as King by pouring olive oil over his head as is written:.
"Then Samuel, with the horn of oil in hand,
anointed him in the midst of his brothers;
and from that day on,
the spirit of the LORD rushed upon David."
(1 Sm 16:13)
This meant that David was chosen by God to lead his people and that the spirit of God was present in his life to guide David in his decisions and to give him strength in the difficulties he would encounter as a leader.