Frowardness [is] in his heart
Or perverse things; evil habits and principles of sin; all manner of wickedness, errors and heresies; things contrary to right reason, repugnant to the will and law of God, and the reverse of sound doctrine; all evil thoughts and evil things; see ( Matthew 15:19 ) ; he deviseth mischief continually;
against his neighbours, and especially against good men; he is continually planning schemes, contriving methods, ways, and means, how to disturb, distress, and ruin men; being a true child of Belial, or of the devil, his heart is the forge where he is continually framing wickedness in one shape or another; and the ground which he is always ploughing up and labouring at to bring forth sin and wickedness, and with which it is fruitful; he soweth discord;
or "strifes" F26: the Syriac version adds, "between two"; which Jarchi interprets between a man and his Maker; rather between a man and his neighbour; between one friend and another; between husband and wife, parents and children, brethren and brethren, magistrates and subjects; between kings and princes of the earth in which sort of work the man of sin, antichrist, has been very busy. The Targum is, "he casteth out strifes", as firebrands among men. The words in the Hebrew text are, "he sendeth out discord", or "strife" F1; these are the messengers sent out by him to make mischief.
The Brenton translation of the Septuagint is in the public domain.