He Declares That There Are Even Now Present Consequences of Sin (Psalms 7:14-16).
‘Behold he exerts himself with iniquity (worthlessness),
Yes, he has conceived mischief, and brought forth falsehood.
He has made a pit and dug it,
And fallen into the trap which he was making.
His mischief will return on his own head,
And his violence will come down on his own pate.'
(It may be that this was to be sung by a different section of the choir to distinguish the change of subject).
While looking for a great act of judgment David does not over look the fact that God judges continually. The ones who exert themselves to what is worthless and evil, and especially to violence (Psalms 7:16), who plan and bring to birth mischief, and deceive men, laying traps for them, will find if they are not careful that they will fall into the hole of deceit that they are digging for others, will find their mischief returning on their own heads, and their violence crushing their skulls. Thus what they sow they will reap.
The pit being dug has in mind the hunter's trap. The picture is of one who digs his pit, and while doing so accidentally falls in even before it is finished.