When you are jealous or envious of others

“A heart at peace gives life to the body, but envy rots the bones.” (Prov. 14:30 NIV)

Jealousy is earthly, unspiritual and demonic

“But if you have bitter jealousy and selfish ambition in your hearts, do not boast and be false to the truth. This is not the wisdom that comes down from above, but is earthly, unspiritual, demonic.” (James 3:14-15 ESV)

Jealousy and envy are works of the flesh  

“For you are still of the flesh. For while there is jealousy and strife among you, are you not of the flesh and behaving only in a human way?” (1 Cor. 3:3 ESV)

Jealousy leads to every vile practice

“For where jealousy and selfish ambition exist, there will be disorder and every vile practice.” (James 3:16 ESV)

A severe warning that includes  Jealousy and envy 

“Now the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God.” (Gal. 5:19-21 ESV)

Therefore.. 

“Set me as a seal upon your heart, as a seal upon your arm, for love is strong as death, jealousy is fierce as the grave. Its flashes are flashes of fire, the very flame of the Lord.” (SOS 8:6 ESV)

“Love is patient and kind; love does not envy or boast; it is not arrogant” (1 Cor. 13:4ESV)

Quotes:

“When there are dissensions, and jealousies, and evil speakings among professors of religion, then there is great need of a revival. These things show that Christians have got far from God, and it is time to think earnestly of a revival.” - Charles Finney

“Envy shoots at others and wounds itself.” - English proverb