Note the behaviour of that friend/enemy, especially his way of speaking, and how his actions belie his speech. His speech is smoother than butter. But his heart is full of battle and warfare. His words are softer than oil, and yet they are like drawn swords
(an uncovered dagger). What a contrast. His language and his thoughts are diametrically opposed to each other. He speaks soothing words, but in his heart, he is out to murder.
The book of Proverbs teaches us a lot about language, the heart, and how much can go wrong in that regard. Proverbs 28:23 reads, Whoever rebukes a man will afterward find more favor than he who flatters with his tongue.
Psalm 5:9 connects with this. It is a prayer for justice against enemies: For there is no truth in their mouth; their inmost self is destruction; their throat is an open grave; they flatter with their tongue.
And Psalm 52:4 speaks about the wicked and how they use their tongue: You love all words that devour, O deceitful tongue.
Let everyone consider the sixth and ninth commandment, with the help of James 3:1–12.
21 His speech was smooth as butter, yet war was in his heart; his words were softer than oil, yet they were drawn swords.