David was an excellent example of "love your enemies". From a human standpoint, it would be understandable for David to rejoice over the death of King Saul. After all, Saul had been hunting David for years, and his death would now clear the way for David to assume the throne for which he had been anointed, and he himself was not responsible for the King's death in any way.
But instead of rejoicing, David mourned. Not only did he mourn, but he killed the man who falsely claimed to have killed the king, thinking the above would be true and he would be rewarded for his efforts. Clearly, David mourned the death of his friend Jonathan more so than the death of Saul, but he took no pleasure in the death of his enemy.
And once again, instead of presuming anything, and despite already knowing he was the anointed king of Israel, David does not rush on ahead. Instead, he again asks for God's guidance.
And things don't start off on a grand scale for David. He is anointed king in the small town of Hebron. But, just like the smallest mustard seed grows into the largest of trees, so too would David's kingdom grow from the tiny town of Hebron to eventually encompass all of Israel and Judah.
David also faced a rival kingship, a rival kingdom.
What a parallel to the spiritual kingdoms on earth today. The kingdom of heaven begun in the hearts of all Christians on earth, and the kingdom of darkness. Which kingdom are you in and to which King do you give allegiance to? There is only One King who sits on the right hand of God - Jesus.
Tomorrow's Bible In a Year Passage passage: 2 Samuel 3-5; 1 Timothy 6