There are valleys to pray in and mountaintops to praise from in the Christian life. Though in our relationship with Christ we should always rejoice (Phil. 4:4; 1 Thess. 5:16) from time to time the believer will find himself in trouble. This trouble can be physical, mental, personal, financial, etc. What are they to do? Because of their ongoing relationship and humility they should pray casting their cares upon the Lord (1 Pet. 5:7; cf Eph. 6:18; Col. 4:2; 1 Thess. 5:17). Calvin speaking on continuous prayer says:
I refer this to moderation of spirit, when the mind keeps itself in calmness under adversity, and does not give indulgence to grief. I accordingly connect together these three things - to rejoice always, to pray without ceasing, and to give thanks to God in all things. For when he recommends constant praying, he points out the way of rejoicing perpetually, for by this means we ask from God alleviation in connection with all our distresses. In like manner, in Phil. 4:4, having said, Rejoice in the Lord always; again I say, Rejoice. Let your moderation be known to all. Be not anxious as to anything. The Lord is at hand. He afterwards points out the means of this - but in every prayer let your requests be made known to God, with giving of thanks. In that passage, as we see, he presents as a source of joy a calm and composed mind, that is not unduly disturbed by injuries or adversities. But lest we should be borne down by grief, sorrow, anxiety, and fear, he bids us repose in the providence of God. And as doubts frequently obtrude themselves as to whether God cares for us, he also prescribes the remedy - that by prayer we disburden our anxieties, as it were, into his bosom, as David commands us to do in Psalm 37:5, and Psalm 55:22; and Peter also, after his example. (1 Peter 5:7). As, however, we are unduly precipitate in our desires, he imposes a check upon them - that, while we desire what we are in need of, we at the same time do not cease to give thanks.
James follows the idea of trouble with that of happiness. Periods of joy follow times of sadness (Psa. 30:5). When the sunshine of God's favor rests upon us, we are filled with cheer and happiness.
The true Church insists on visiting, caring, and praying for the sick and does not abandon them (Matt 25:36). That the elders were to be called to the sick person and that their prayers would save the person "from death" (Jas. 5:20) probably indicate that James had in mind cases of extreme cases of illness believed to be caused by sin in the person's life. There are implications, however, for many other uses of intercessory prayer and confession to elders (Acts 14:23; Titus 1:5). As to the phrase "anoint him with oil" it is commonly misused today by those of the Word of Faith Movement. See "Why Do Christians Need Doctors?" and "Share.... in my troubles - Philippians 4:14" below. Olive oil had a common medicinal use in the ancient world (Mark 6:13; Luke 10:34), but here the oil had a symbolic use in reference to the healing power of God.
Whether a member of the congregation is suffering, or they are cheerful, James directs both to God in prayers of petition and praise, respectively. After this general instruction, James addresses the sick specifically. First, a sick member should call the elders of the community to pray over him or her. Elders are synonymous with overseers or bishops (Acts 20:17, 28; Tit. 1:5, 7; 1 Pet. 5:1-2), who are called by God to intercede regularly for the congregation (see Acts 6:3-4)). Second, the elders should anoint him with oil in the name of the Lord. While olive oil had a common medicinal purpose in the ancient world (see Mk 6:13 and Lk 10:34), anointing was also symbolic of the Holy Spirit’s presence and blessing. The consecration of people and objects with oil was required in the Old Testament (Ex. 40:13, 15; Num. 3:3). Thus, James instructs the leaders of the church to consecrate the sick person for God’s purposes. Doing so in the name of the Lord attributes the healing power to the Lord and not to the oil or to the elders.