Apostle Paul assertion in verse 3 of Romans chapter 6, ' Know ye not', sounds as if these Roman Christians were not taught the spiritual implications of the Baptism which they had received and the obligations expected of them thereafter. Some of these spiritual realities that take place at Baptism are (i) we are dead with Christ ( ii) we have resurrected with Him ( iii ) our old man is crucified with Him ( iv) we are dead to sin, and ( v ) we shall live with Christ.
The expected response from these spiritual realities therefore is what we should walk in newness of that new life we have received. Be no more slaves to sin, and live unto God henceforth ( Romans 6:4,6,10-11 ).
https://youtu.be/aGuYZSfyI-g?si=kV-tqverOqc4NSr7
Many people view Christian baptism as a mere fulfilment of all righteousness and so do not live in confidence of the spiritual realities mentioned earlier. The advice for us remains that we must learn to live to meet the expectations God wants us as a result of our Baptism by walking in the newness of life Christ imputed in us, everywhere we find ourselves, so that when Christ shall appear, we shall also appear before Him spotless ( 1John 3:3-10 )