Chapter twelve deals with Samuel's speech to the people. In it, Samuel testifies as to his integrity. He never took anything that was not given to him, and he also reproached the people for their ingratitude to God in asking Him for a king like the heathen nations. He then frightened them by asking God for thunders and rains in harvest time to confirm that this was great in the eyes of Jehovah, and finally, he consoled them by telling them of God's mercy and love for them.
But in his speech, as a good preacher, Samuel instructs them in one thing that the people should never let go of or forget about their lives, if they want the mercy of God to remain on them.
Twice in Samuel's speech before the people he says the same thing to them. “But serve the Lord with all your heart.”
When Samuel says with all your heart, he means to serve God with enthusiasm and sincerity. The phrase with all your heart, deals with doing things with a desire, with love, voluntarily, not by force or by responsibility, or because I must ... Nothing pleases God more than when we do thing for HIM, with all of our heart.
Colossians 3:18-24 Wives, submit yourselves unto your own husbands, as it is fit in the Lord. Husbands, love your wives, and be not bitter against them. Children, obey your parents in all things: for this is well pleasing unto the Lord. Fathers, provoke not your children to anger, lest they be discouraged. Servants, obey in all things your masters according to the flesh; not with eyeservice, as men pleasers; but in singleness of heart, fearing God: And whatsoever ye do, do it heartily, as to the Lord, and not unto men; Knowing that of the Lord ye shall receive the reward of the inheritance: for ye serve the Lord Christ.
Eph 6:7 With good will doing service, as to the Lord, and not to men:
Samuel wanted at the end of his speech, for the people to understand why it was important to serve God with all your heart.
Why we should serve God with all of our heart:
1. Because of sacrifice that God made by sending his Son to die on the cross for us.
Samuel reminds them that they should serve the Lord with all their hearts, because of the ransom that God sent, so that they would be free from all oppression.
Today you and I should serve God with all of our hearts for the sacrifice that God made by sending his Son to die on the cross for us. That sacrifice should be reason enough to serve Him with all our hearts. The fact that one day we are going to go to Heaven when we die, and not Hell, should make us feel that we are indebted to Him.
Deuteronomy 11:1-7 Therefore thou shalt love the LORD thy God, and keep his charge, and his statutes, and his judgments, and his commandments, alway. And know ye this day: for I speak not with your children which have not known, and which have not seen the chastisement of the LORD your God, his greatness, his mighty hand, and his stretched out arm, And his miracles, and his acts, which he did in the midst of Egypt unto Pharaoh the king of Egypt, and unto all his land; And what he did unto the army of Egypt, unto their horses, and to their chariots; how he made the water of the Red sea to overflow them as they pursued after you, and how the LORD hath destroyed them unto this day; And what he did unto you in the wilderness, until ye came into this place; And what he did unto Dathan and Abiram, the sons of Eliab, the son of Reuben: how the earth opened her mouth, and swallowed them up, and their households, and their tents, and all the substance that was in their possession, in the midst of all Israel: But your eyes have seen all the great acts of the LORD which he did.
2. For ALL that God has done for us and does every day
THINKING of all that God has done and will continue to do in us, should motivate us to never stop serving Him with all our hearts. God has been very good to us.
1 Corinthians 15:10 But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I laboured more abundantly than they all: yet not I, but the grace of God which was with me.
2 Corinthians 3:5 Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God;
3. Because serving God is a great privilege
And by the way, Jesus was God in the flesh, and did not come to be served, but to serve—and He did it with all the Heart.
Philippians 2:3-11 Let nothing be done through strife or vainglory; but in lowliness of mind let each esteem other better than themselves. Look not every man on his own things, but every man also on the things of others. Let this mind be in you, which was also in Christ Jesus: Who, being in the form of God, thought it not robbery to be equal with God: But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men: And being found in fashion as a man, he humbled himself, and became obedient unto death, even the death of the cross. Wherefore God also hath highly exalted him, and given him a name which is above every name: That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth; And that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.