I believe the answer to your good question can begin to be found in James 5:14-16, “Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord: And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him. Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.”

We learn here the importance of prayer for one another.  If one is sick, he is instructed to call for the elders of the local church.  They will come and pray for him and anoint him with oil in the name of the Lord.  In the assembly, it is the elders who take the oversight and seek to minister to the needs of those local saints. We read a little about the function of the elders in 1 Peter 5:1-2 which says, “The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed: Feed the flock of God which is among you, taking the oversight thereof, not by constraint, but willingly; not for filthy lucre, but of a ready mind.”  It is normal that if one was in need of prayer, he would desire men of seriousness and soundness in the faith, persons of long standing and experience to intercede to the Lord on his behalf. 

Here, the use of oil is pointed out.  Only once in the Bible is ‘holy water’ mentioned.  Numbers 5:17 says, “And the priest shall take holy water in an earthen vessel; and of the dust that is in the floor of the tabernacle the priest shall take, and put it into the water.  In all likelihood, this refers to water that had been taken from the laver, which was part of the furniture of the Tabernacle.  There are no special powers connected to this holy water.  Today, water is considered holy when it has been blessed by a Catholic priest.  This is Catholic tradition, not Biblical teaching. 

What is the purpose of anointing a sick person with oil?  The oil obtained from the olive was much in use among the ancient Jews, both as an article of food, and as a medical remedy.  It was also employed in many civil and religious ceremonies. The good Samaritan Is represented as employing it in the case of the wounded traveler (Luke 10:30-34), and the twelve disciples, when sent out upon their original mission, anointed with oil the sick whom they were called upon to cure. (Mark 6:7-13). 

Anointing the sick with oil in the name of the Lord was symbolic to show this action was being taken on behalf of the Lord Jesus Christ.  To anoint in the name of the Lord is to attribute to the Lord the healing that would come upon the sick one.  We need to be careful to notice that the laying on of hands, or the anointing of oil is not what would heal the sick one.  James 5:15 is emphatic in saying, “And THE PRAYER OF FAITH shall save the sick.”  It is a faithful servant praying faithfully to the Lord that can bring about healing to the sick.  Verse 16 tells us plainly, “The effectual fervent prayer of a righteous man availeth much.”  The earnest prayer of a believer on the Lord Jesus produces much results.  Perhaps it may result in the healing of the sick, if it is the Lord’s will.  We read in 1 John 5:14, “And this is the confidence that we have in him, that, IF WE ASK ANY THING ACCORDING TO HIS WILL, he heareth us.” 

Fasting and praying are often linked together in the Bible, such as what we read in Matthew 17:21, “Howbeit this kind goeth not out but by prayer and fasting.”  The practice of fasting is deny yourself any food for a period of time.  This was a way of showing dedication to the Lord and denial of self.  It is mentioned with prayer to show a person’s great dedication and fervency when he prays. 

One good take-away from this mediation is to see the importance that we “pray one for another.”  When we join our hearts and voices together to petition the Lord for our needs, He will hear us and will answer according to His loving and perfect will.  (470.2)