The prophet Samuel was God's faithful servant all the days of his life. For the greater part of his ministry, Israel was still a Theocracy – God ruled over the nation. Samuel provided leadership during that time and is often considered the last of the judges. But in 1 Samuel 8, the people expressed their desire for a king to reign over them "like all the other nations." When Samuel took the matter to the Lord he was told that the people had not rejected him but had rejected God's rule over them.
God warned the people what their desire for a king would lead to, but the people ignored Him, and God gave them what they wanted. Saul is anointed in chapters 9-10 and leads Israel into battle in chapter 11.
In 1 Samuel 12, Samuel addresses the nation and reproves them for rejecting God's rule over them (v. 12). He calls down thunder and rain on the day of wheat harvest, proving to Israel their great wickedness (vv. 17-18). The people become fearful and ask Samuel to pray for them (v. 19).
Samuel's response is instructive, and it'd do us well to familiarize ourselves with the simple, all-important truths laid out in his sermon:
1 Samuel 12:20 And Samuel said unto the people, Fear not: ye have done all this wickedness: yet turn not aside from following the LORD, but serve the LORD with all your heart;
Samuel reminds them that past failures are no excuse to go on failing but provide reason to get up and keep pressing toward the mark (Proverbs 24:16; Philippians 3:14).
1 Samuel 12:21 And turn ye not aside: for then should ye go after vain things, which cannot profit nor deliver; for they are vain.
Samuel reminds them of the emptiness, the vanity, the meaninglessness of following anything or anyone but the Lord (Ecclesiastes 1:14; John 6:68; 2 Corinthians 4:18; Mark 8:36-37).
1 Samuel 12:22, 24 For the LORD will not forsake his people for his great name's sake: because it hath pleased the LORD to make you his people…Only fear the LORD, and serve him in truth with all your heart: for consider how great things he hath done for you.
Being mindful of the Lord's love, His provision, and His promise to never forsake us are enough to make us want to keep giving Him our all (Romans 12:1-2; Hebrews 13:5; 2 Corinthians 5:14; 1 John 4:19).
1 Samuel 12:23 Moreover as for me, God forbid that I should sin against the LORD in ceasing to pray for you: but I will teach you the good and the right way:
May we be faithful to pray for one another, to encourage and exhort one another – that God would plant these simple truths in our minds and burn them in our hearts and keep us walking in the light of His truth (1 Thessalonians 5:17, 25; Hebrews 3:13; 1 Timothy 4:12).