15 But You, O Lord, are a God full of compassion, and gracious,
Longsuffering and abundant in mercy and truth.
16 Oh, turn to me, and have mercy on me!
Give Your strength to Your servant,
And save the son of Your maidservant.
17 Show me a sign for good,
That those who hate me may see it and be ashamed,
Because You, Lord, have helped me and comforted me. (Psalm 86: 15-17 NKJV)
In this prayer of David, he is acknowledging attributes of God's great heart and asking God to reveal these attributes to him on a personal level so that he can then be a witness of them to others. Put another way David is saying--"Out of Your great compassion, longsuffering, abundantly merciful and truthful heart, express to me personally these great attributes of Yours, implant them in me, so that I may be a testimony and witness of them in the lives of others"!