Yes cursing is a sin against God.
With the tongue we praise our Lord and Father, and with it we curse men, who have been made in God's likeness. Out of the same mouth come praise and
cursing. My brothers, this should not be. Can both fresh water and salt water flow from the same spring? My brothers, can a fig tree bear olives, or a
grapevine bear figs? Neither can a salt spring produce fresh water.
Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit
those who listen.
1 Peter 3:10
For, "Whoever would love life and see good days must keep his tongue from evil and his lips from deceitful speech.