1. Love God and Christ. (Jos 23:6,8,11)
    1 Cor 16:22, Gal 1:7-9

In the Old Testament, Joshua commanded the Israelites to keep all the Law of Moses and to love God. (Joshua 23:6,8,11)

Joshua 23:6 Be ye therefore very courageous to keep and to do all that is written in the book of the law of Moses, that ye turn not aside therefrom to the right hand or to the left;
8 But cleave unto the Lord your God, as ye have done unto this day.
11 Take good heed therefore unto yourselves, that ye love the Lord your God.

Anyone who does not love Jesus, the Christ, will be cursed. (1 Corinthians 16:22)

1 Corinthians 16:22 If any man love not the Lord Jesus Christ, let him be Anathema Maranatha.

Also, those who preach any gospel other than that Jesus is the Christ will be cursed. (Gal 1:7-9)

Gal 1:7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
9 As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed.