From the additional notes to Charles Spurgeon's The Treasury of David; notes on Psalm 108.
Verse 1. Meditation is a fixed duty. It is not a cursory work. Man's thoughts naturally labour with a great inconsistency; but meditation chains them, and fastens them upon some spiritual object. The soul when it meditates lays a command on itself, that the thoughts which are otherwise flitting and feathery should fix upon its object; and so this duty is very advantageous. As we know a garden which is watered with sudden showers is more uncertain in its fruit than when it is refreshed with a constant stream; so when our thoughts are sometimes on good things, and then run off; when they only take a glance of a holy object, and then flit away, there is not so much fruit brought into the soul. In meditation, then, there must be a fixing of the heart upon the object, a steeping the thoughts, as holy David: "O God, my heart is fixed." We must view the holy object presented by meditation, as a limner who views some curious piece, and carefully heeds every shade, every line and colour; as the Virgin Mary kept all these things, and pondered them in her heart. Indeed; meditation is not only the busying the thoughts, but the centring of them; not only the employing of them, but the staking them down upon some spiritual affair. When the soul, meditating upon something divine, saith as the disciples in the transfiguration (Mt 17:4), "It is good to be here."—John Wells, in the "Practical Sabbatarian," 1668.