With Saul the hatred was manifest, it was not hidden. With many Christians the same jealousy, the same hatred, lurks in the heart even though it is not blatantly demonstrated in their deeds as was Saul's.
He that hateth dissembleth with his lips ... when he speaketh fair, believe him not: for there are seven abominations in his heart, whose hatred is covered by deceit,... A lying tongue hateth those that are afflicted by it (Prov. 26:24-28).
The bitter ill-will that you nurse in your heart
Will not stay inside where it first got its start:
For sinew and blood are a thin veil of lace —
What you wear in your heart you wear on your face.
Jealousy and ill-will harbored in the heart toward another breed deceitfulness. Being two-faced is all too common among us. Shameful is the Judas kiss. "One speaketh peaceably to his neighbor with his mouth, but in his heart he layeth his wait" (Jer. 9:8). "Believe them not, though they speak fair words unto thee" (Jer. 12:16). "The words of his mouth were smoother than butter, but war was in his heart" (Psa. 55:21). "With their mouth they show much love, but their heart..." (Ezek. 33:31). "They hunt every man his brother with a net" (Mic. 7:2). "Lay a snare for him" (Isa. 19:21).
"Sowing discord (promoting a clash or disharmony) among brethren" God hates (Prov. 6:19). Speaking evil (disparagement, tearing one another apart, ridiculing) of one another He forbids (James 4:11; Gal. 5:15). Both involve a motive unworthy of a Christian, that of exalting self at the expense of another. "Why dost thou set at naught thy brother?" (Rom. 14:10). "The Lord...will bring to light the hidden things of darkness, and will make manifest the counsels of the hearts."