Romans 3:1
What special privilege, then, has the Jew? Or what is the use of circumcision?
Romans 2:25-29
Circumcision does indeed profit, if you are obedient to the Law; but if you habitually break the Law, your circumcision is become uncircumcision.
1 Corinthians 15:32
If after the manner of men I have fought with wild beasts at Ephesus, what good does it do me? If the dead do not rise, Let us eat and drink, For we shall be dead tomorrow.
Hebrews 13:9
Do not allow yourselves to be swept away by various and strange teachings. For it is a beautiful thing to be established in heart by grace, and not by regulations regarding food, from which those that occupied themselves with them have derived no benefit.