We have earlier looked at what Jesus says about this in another Gospel. Here is Matt 15:17-20:
17Do you not see that whatever goes into the mouth passes into the stomach and is expelled? 18But what comes out of the mouth proceeds from the heart, and this defiles a person. 19For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false witness, slander. 20 These are what defile a person. But to eat with unwashed hands does not defile anyone.”
In this psalm it says in verses 3 and 4:
3 Set a guard, O LORD, over my mouth;
keep watch over the door of my lips!
4 Do not let my heart incline to any evil,
to busy myself with wicked deeds
in company with men who work iniquity,
and let me not eat of their delicacies!
In Matt. 15 Jesus is picking up the theme in these verses and points to the link between the mouth and the evil of the heart. David asks for the LORD’s help against the threat from within – the heart and the expression this takes in words spoken by the mouth.
The verses that follow in the psalm are an awesome Gospel witness (v.5-6):
5 Let a righteous man strike me—it is a kindness;
let him rebuke me—it is oil for my head;
let my head not refuse it.
Yet my prayer is continually against their evil deeds. 6When their judges are thrown over the cliff,
then they shall hear my words, for they are pleasant.
If we take correction from a righteous man it is good for us. This is true in part of our human experience – we are ready to receive rebuke only from people who practice what they teach! But what man is truly righteous and without fault? Who can we entrust to assess our whole life? No one!
Well actually one – Jesus! He was, and is truly righteous. If we let Him rebuke us and correct us, it is a blessing that is to our benefit in the long run. However, if we reject and rebel against is words, and stumble on account of Him, then we will waste away in our own ignorant and foolish ways.
Interestingly the translation of v. 6 can look quite different, as indeed the alternative translation of the ESV suggests: “When their judges fall into the hands of the Rock”. This is the most straight forward translation of the Hebrew, and in my view as such it is the better one.
Not only is it closer to the Hebrew, but with the alternative translation of the verse makes more sense: When the evil rulers fall into the hands of God – the Rock – then all will hear the plight of the oppressed.