I like what most of our brothers and sisters in Christ have said so far, but I would remind all that through baptism is how we are born again. Buried in His death, and risen to a new life with a spiritual mindset.
The other thing I would pose to people is you must follow the greatest command to enter into heaven;
Matthew 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.
Then our Lord Jesus said that if you believe in Him, and love Him you will do what He said, not just hear, and He commanded baptism;
John 14:15
"If you love Me, you will keep My commandments.
Luke 6:47
Whosoever cometh to me, and heareth my sayings, and doeth them,
Mark 16:16
He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
Matthew 28:19
Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,
Then we have James and Paul telling us that if we fail to do something, or use being under grace as an excuse to do or not do something then it is sinful;
James 4:17
Therefore, to one who knows the right thing to do and does not do it, to him it is sin.
Galatians 5:13
For, brethren, ye have been called unto liberty; only use not liberty for an occasion to the flesh, but by love serve one another.
( Also read Romans 6 )
So by what we see James and Paul saying we can see that we are not to use grace as an excuse to sin, and we also are not to use other examples as Peter when he denied Christ to say we can to at hard times. And definitely not use the thief on the cross for a reason to not be baptized, for the thief did not have the time to get baptized, plus he is not an example of the new covenant as it was not issued in tell after Jesus crucifixion.
Hebrews 9:16
For where a testament is, there must also of necessity be the death of the testator.