Hi KRose, 2000 years ago God was in Christ, reconciling the world unto Himself, not imputing our trespasses unto us (2 Corinthians 5:19 KJV). Paul writes that the gospel of Christ (1 Corinthians 15:1-4 KJV) is the power of God unto salvation to every one that believeth (Romans 1:16 KJV). All trespasses were forgiven then whether or not you believe it (Romans 3:3 KJV, Colossians 2:13 KJV), but in order for Christ's work to be put to your account, you must believe it (Romans 3:21-22 KJV, Romans 4:24-25 KJV).
Jesus did not teach "only believe".
Jesus taught--
Mat 7:24 Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock:
Mat 7:25 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell not: for it was founded upon a rock.
Mat 7:26 And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand:
Mat 7:27 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it.
One must rightly divide Gods Word.
Peter said--
2Pe 3:15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;
2Pe 3:16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
2Pe 3:17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.
2Pe 3:18 But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen.
LA