As a Christian is grinding a sin And also if the answer is yes is there a specific biblical verse which says it's a sin?

Answer 1

You will need to be more specific concerning the term Grinding in the English

If you are talking about Grinding between or upon a stone then the answer is no its not a sin. Grinding stones are common simple tools.

Answer 2

Grinding is masturbation.

But I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart. (Matthew 5:28)

Let us behave properly as in the day, not in carousing and drunkenness, not in sexual promiscuity and sensuality, not in strife and jealousy. But put on the Lord Jesus Christ, and make no provision for the flesh in regard to its lusts. (Romans 13:13-14)

But I say, walk by the Spirit, and you will not carry out the desire of the flesh. For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. (Galatians 5:16-17)

For all that is in the world, the lust of the flesh and the lust of the eyes and the boastful pride of life, is not from the Father, but is from the world. (1 John 2:16)