The law of the fast is an ancient law. God's people from the time of Adam have used this law to draw nearer to God and to worship Him. To fast properly means to go without food and drink voluntarily for a certain period of time. To prepare yourself and others to receive God's blessings, you must combine fasting with prayer.
Jesus Christ indicated the importance of fasting by His personal example when He fasted for forty days in the wilderness. (See Luke 4:1-4.) He taught His disciples about the power of prayer and fasting when He cast a devil out of a child. When His disciples questioned, "Why could not we cast him out?" Jesus replied, "Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you. Howbeit this kind goeth not out but by prayer and fasting." (See Matthew 17:14-21.)
This account teaches how prayer and fasting go together to strengthen us in our personal efforts to live the gospel of Jesus Christ and to bless the lives of other people. When attempting to overcome a weakness or sin, especially after an extended time of struggling with the problem, we may need to add fasting to your prayers for help. The problem may be like the example above and be the kind the goes out only through prayer and fasting.
Fasting means to go without food and drink, and an occasional fast is good for the body and invigorates the mind. I once worked with a woman who "fasted" (going without food) one day each week in order to cleanse her body. She understood that fasting helped her physical body, but she did not understand that fasting could also benefit her spiritually. A purposeful fast is more than simply going without food and drink; it also includes a need to concentrate on spiritual things.
Going without food or drink is simply starving our bodies. There are many people who use this type of fast to draw attention to something or someone. Other people think that they are "fasting" when they are simply starving. In order to benefit the whole soul, fasting must be accompanied by sincere prayer. Each fasting period should start and end with prayer. To make the fast even more beneficial, it should have a purpose. Fasting accompanied by sincere prayer can be used to overcome weaknesses and to solve problems. We can fast and pray for help or guidance for ourselves or for others who may be ill, injured, or otherwise in need of a blessing. Fasting can help us know the truth, become more humble and feel closer to Heavenly Father. It can also bring comfort in times of sorrow and mourning. (See Mosiah 27:22-23 and Alma 28:4-6.) We should be cheerful when we fast. We should not advertise the fact that we are fasting to others nor fast to impress others. (See Matthew 6:16-18.)
The Savior taught the true form of fasting in His Sermon on the Mount. He described hypocrites as those who, when they fast, "disfigure their faces, that they may appear unto men to fast." Instead of trying to impress the people around us by our appearing to fast, we should fast "unto thy Father which is in secret: and thy Father, which seeth in secret, shall reward thee openly" (Matthew 6:16-18).
Isaiah, the Old Testament prophet, taught the people of his day - and ours - of the true spirit of the fast: "Is not this the fast that I have chosen? To loose the bands of wickedness, to undo the heavy burdens, and to let the oppressed go free, and that ye break every yoke? Is it not to deal thy bread to the hungry, and that thou bring the poor that are cast out to thy house? when thou seest the naked, that thou cover him; and that thou hide not thyself from thine own flesh?" (Isaiah 58:6-7).
The prophet Isaiah also taught about the many blessings that come by obeying the law of the fast: "Then shall thy light break forth as the morning, and thine health shall spring forth speedily: and thy righteousness shall go before thee; the glory of the Lord shall be thy rereward. Then shalt thou call, and the Lord shall answer; thou shalt cry, and he shall say, Here I am…. If thou draw out thy soul to the hungry, and satisfy the afflicted soul; then shall thy light rise in obscurity, and thy darkness be as the noonday: and the Lord shall guide thee continually, and satisfy thy soul in drought, and make fat thy bones: and thou shalt be like a watered garden, and like a spring of water, whose waters fail not" (Isaiah 58:8-11).
To properly observe the fast we should go without food or drink for two consecutive meals. We should not fast too frequently or for excessively long periods of time. The Church of Jesus Christ of Latter-day Saints designates one Sunday each month - which is usually the first Sunday - as a day for fasting. Members of the Church are taught that a proper observance of fast Sunday includes attendance at fast and testimony meeting and giving a fast offering to help care for those in need as well as going without food and drink for two consecutive meals. Of course, members of the Church can also fast at other times for special blessings for themselves or others.
I know by personal experience that fasting brings many blessings. It improves our lives, gives us increased strength, and helps us to live other principles of the gospel by drawing us closer to God. It helps us improve our character as we learn to control our appetites and passions. Fasting helps us to prove to ourselves that we have self-control. Children can learn to develop spiritual strength if we teach them to observe a proper fast.
Wise and prayerful fasting helps us develop faith, and increased faith brings greater spiritual power. The Savior promised that proper fasting brings blessings from God: "Thy Father, which seeth in secret, shall reward thee openly" (Matthew 6:18).