Ecc 12:1-2, Mt 22:37-38, Jn 6:29, Jn 17:3, Jn 3:16
In the Old Testament, what God required of the people of Israel was to fear God and keep the law that God commanded. (Deut 10:12-13, Ecclesiastes 12:1-2)
Deut 10:12 And now, Israel, what doth the Lord thy God require of thee, but to fear the Lord thy God, to walk in all his ways, and to love him, and to serve the Lord thy God with all thy heart and with all thy soul, 13 To keep the commandments of the Lord, and his statutes, which I command thee this day for thy good?
Ecclesiastes 12:1 Remember now thy Creator in the days of thy youth, while the evil days come not, nor the years draw nigh, when thou shalt say, I have no pleasure in them; 2 While the sun, or the light, or the moon, or the stars, be not darkened, nor the clouds return after the rain:
To love God is the first commandment. (Mt 22:37-38)
Mt 22:37 Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. 38 This is the first and great commandment.
God sent his only begotten son Jesus to this earth to do the work of Christ in order to save us. (John 3:16)
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
It is God's work to believe in Jesus, the one sent by God, as the Christ. (John 6:29, John 17:3)
John 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
John 17:3 And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.