"He that loveth pureness of heart, for the grace of his lips the king shall be his friend."
Two personal issues are vital to good friendships, a pure heart, and a gracious talk. If our heart is not “pure” then our motives will be questionable. If our speech is not kind, it won’t be very easy to have friends. These two qualities are a must for good relationships to develop.
“He that loveth pureness of heart.”
Being a human with sin issues, this is a tall order to fill. Unless the Lord is intervening in our lives, it will be impossible for us to have “pure hearts.”
“The heart is deceitful above all things, and desperately wicked: who can know it?” (Jeremiah 17:9).
Without a “new heart” from the Lord after salvation, we have no hope of having a pure heart. After our salvation, we believers still contend with our “old man” daily. Unless we have the help of the Holy Spirit and the Word of God, our flesh leads us away from God, to do and think things that are un-Christlike, and definitely “impure.” Our text indicates that we are to “love pureness of heart.” It is our desire to have a heart that honors God. This is our wish, our pursuit, and our goal.
Jesus has taught us that a “pure heart” is necessary to see The King!
“Blessed are the pure in heart: for they shall see God” (Matthew 5:8).
Having a heart that’s striving for purity, is a start to good friendships, but we need more than a right spirit.
Right words come from a good heart and evil words from a wicked heart. To be a good friend, we need to use good words.
“For the grace of his lips, the king shall be his friend.”
The way we talk with the king should be the way we speak with others.
“Righteous lips are the delight of kings, and they love him that speaketh right” (Proverbs 16:13).
“pureness of heart — and gentle, kind words win favor, even from kings.” 
In prophecy, the coming Messiah, Jesus Christ, is seen to be the God-Man with gracious speech.
“Thou art fairer than the children of men: grace is poured into thy lips: therefore God hath blessed thee forever” (Psalm 45:2).
Jesus, the Good Shepherd, was known for His gracious speech, even as a young man.
“And all bare him witness and wondered at the gracious words which proceeded out of his mouth. And they said, Is not this Joseph’s son?” (Luke 4:22).
When David was looking for people to serve in his court, here’s what he was looking for.
“Mine eyes shall be upon the faithful of the land, that they may dwell with me: he that walketh in a perfect way, he shall serve me” (Psalm 101:6).
Believers, we need to be guarding our pure heart and speak gracious words as we serve the King today.
 Jamison, Fausset, and Brown. Jamison-Fausset-Brown’s Commentary, the electronic version in eSword.