Pray (verb):

The first time that the word "pray" is found in scripture is in Genesis 20:7.  The English verb "pray" is from the Hebrew word #6419 "palal" (pronounced paw-lal'), which means to intreat, judge or make supplication (Strong's Greek/Hebrew Dictionary).  According to Vine's Expository Dictionary of Hebrew words, the word "palal" means to intervene, mediate, judge.  Vine's goes on to say:

"The first occurrence of palal in the Old Testament is in Genesis 20:7, where the reflexive or reciprocal form of the verb expresses the idea of "interceding for, prayer in behalf of": "...he shall pray for thee...." Such intercessory praying is frequent in the Old Testament: Moses "prays" for the people's deliverance from the fiery serpents (Numbers 21:7); he "prays" for Aaron (Deuteronomy 9:20); and Samuel "intercedes" continually for Israel (1 Samuel 12:23). Prayer is directed not only toward Yahweh but toward pagan idols as well (Isaiah 44:7). Sometimes prayer is made to Yahweh that He would act against an enemy: "That which thou hast prayed to me against Sennacherib king of Assyria I have heard" (2 Kings 19:20)."

"Just why this verb form is used to express the act of praying is not completely clear. Since this verb form points back to the subject, in a reflexive sense, perhaps it emphasizes the part which the person praying has in his prayers. Also, since the verb form can have a reciprocal meaning between subject and object, it may emphasize the fact that prayer is basically communication, which always has to be two-way in order to be real. (from Vine's Expository Dictionary of Biblical Words - Copyright (C) 1985, Thomas Nelson Publishers)

Although Genesis 20:7 is the first time that "palal" is recorded, it is in Genesis 4:26 that men began to "call upon the name of the Lord;" which is another way to express prayer to God or entreating God. 

Prayer (noun):

The first time the word prayer (noun) is found in scripture is in 1 Kings 8:28.  The English noun "prayer" is from the Hebrew word #8605 "tephillah" (pronounced tef-il-law') which means intercession or supplication.

Question:

According to Vine's Expository Dictionary, the Hebrew word "palal" expresses the idea of: (give the best answer below)

1. Interceding for someone.
2. Prayer in behalf of someone.
3. Both.