"1Blessed is the man that walketh not in the counsel of the ungodly, nor standeth in the way of sinners, nor sitteth in the seat of the scornful.
"2But his delight is in the law of the LORD; and in his law doth he meditate day and night." (Psalm 1: 1-2)
We can meditate on His Law, because He has written His laws in our hearts and minds because of the Holy Spirit:
"10For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:
By seeing more of Jesus Christ in our lives, we meditate on the Living Word (1 Peter 1: 23), or the Word made flesh (John 1: 14).
The more that we grow in grace and knowledge of the Lord (2 Peter 3:18), we are meditating on Jesus Christ, the Word made flesh who lives in everyone of us (Colossians1: 27).