Thanks for your question!
Cursing is the opposite of blessing, expressing the desire that the recipient of the curse will experience evils associated with the disfavour of God.
In the Bible, blessings and curses are related; the book of Deuteronomy prescribes that obedience to the Law of Moses would bring God's blessing on the nation of Israel. Conversely disobedience would bring God’s curse.
Both the blessings and the curses are written out so that Israel were left in no doubt as to the consequences of both obedience and disobedience.
Deuteronomy 11:26 Behold, I set before you this day a blessing and a curse; 27 A blessing, if ye obey the commandments of the LORD your God, which I command you this day: 28 And a curse, if ye will not obey the commandments of the LORD your God, but turn aside out of the way which I command you this day, to go after other gods, which ye have not known.
In Deuteronomy 27 Moses gives the commandment that when they go into the land of Canaan the blessing and cursing are to be spelled out in a singular manner.
Deuteronomy 27:12 These shall stand upon mount Gerizim to bless the people, when ye are come over Jordan; Simeon, and Levi, and Judah, and Issachar, and Joseph, and Benjamin: 13 And these shall stand upon mount Ebal to curse; Reuben, Gad, and Asher, and Zebulun, Dan, and Naphtali.
This is recorded as being done in Joshua 8:33-35.
The blessings and curses are detailed in Deuteronomy 27 and 28.
The history of Israel shows how accurately these blessings and curses have been, and are still being, fulfilled.
What we need to realise is that there is no supernatural power other than God. We cannot be blessed or cursed without it being in accordance with the will of God.
Proverbs 26:2 As the bird by wandering, as the swallow by flying, so the curse causeless shall not come.
A curse would not come on Israel unless they earned it by their behaviour. This becomes clear when Balak hires Balaam to curse Israel in Numbers 22 and 23.
Numbers 23:8 How shall I curse, whom God hath not cursed? or how shall I defy, whom the LORD hath not defied?
One of the most important blessings in the Old Testament is that given to Abraham.
Genesis 22:17 That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies; 18 And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.
Paul says that this blessing is the basis of the gospel because the seed is Christ.
Those then that believe the gospel and are baptised into Christ are blessed by God through him. This is the difference between the Old Covenant in the Law of Moses and the New Covenant in Christ. Those who tried to live by the Law of Moses would always fail in some point and one failure brought upon them the curse of the Law.
Galatians 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them. (Quoting Deuteronomy 27:26)
In the Law there was a clause which brought the curse of the Law upon Christ even though he had fulfilled the Law in all points in that he did not sin.
Deuteronomy 21:23 His body shall not remain all night upon the tree, but thou shalt in any wise bury him that day; (for he that is hanged is accursed of God;) that thy land be not defiled, which the LORD thy God giveth thee for an inheritance.
By being hanged on a tree the curse of the Law was brought upon him who God would not curse.
Galatians 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
In raising Christ from the dead God put aside the Law of Moses and redeemed those that are baptised into Christ from the Law of sin and death.
Romans 8:1 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
If there is no condemnation from God there can be no curse. Christ came then to bless us ‘In thy seed shall all nations be blessed’.
Matthew 5:3 Blessed are the poor in spirit: for theirs is the kingdom of heaven. 4 Blessed are they that mourn: for they shall be comforted. 5 Blessed are the meek: for they shall inherit the earth. 6 Blessed are they which do hunger and thirst after righteousness: for they shall be filled. 7 Blessed are the merciful: for they shall obtain mercy. 8 Blessed are the pure in heart: for they shall see God. 9 Blessed are the peacemakers: for they shall be called the children of God. 10 Blessed are they which are persecuted for righteousness’ sake: for theirs is the kingdom of heaven. 11 Blessed are ye, when men shall revile you, and persecute you, and shall say all manner of evil against you falsely, for my sake.
Having then been blessed in Christ we are instructed to bless others whether they deserve a blessing or not.
Matthew 5:44 But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
Romans 12:14 Bless them which persecute you: bless, and curse not.
1 Corinthians 4:12 And labour, working with our own hands: being reviled, we bless; being persecuted, we suffer it:
James 3:8 But the tongue can no man tame; it is an unruly evil, full of deadly poison. 9 Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitude of God. 10 Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be.
1 Peter 3:9 Not rendering evil for evil, or railing for railing: but contrariwise blessing; knowing that ye are thereunto called, that ye should inherit a blessing.
We need fear no curse, because God loves us.
Romans 8:31 What shall we then say to these things? If God be for us, who can be against us? 32 He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things? 33 Who shall lay any thing to the charge of God’s elect? It is God that justifieth. 34 Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us. 35 Who shall separate us from the love of Christ? shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? 36 As it is written, For thy sake we are killed all the day long; we are accounted as sheep for the slaughter. 37 Nay, in all these things we are more than conquerors through him that loved us. 38 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, 39 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
I hope this helps!