Psalm 27:4 says “One thing I have asked of the Lord, that I shall seek …”. Notice the two important phrases here: “I have asked …” and “I shall seek”. Each of these actions is important, and necessary in its own way, for we find here both the divine and human elements in the equation of receiving something we desire: first of all realizing that every good gift comes from God — you must ASK it from Him. But then we are not merely to ask it of God; we are also to SEEK that thing actively.
Many people make a mistake by “merely” asking God, but then doing nothing practical to seek what they desire — for example, the person who asks for a job but is not out actively pursuing employment. Others err by merely doing the best they can at seeking, but then making a vital mistake by not asking God, the Giver of all good gifts, to do what only He can do to help them.
In the original context of Psalm 27, David applied both of these elements to his desire to know God. That “one thing” he desired was “to behold the beauty (literally, “delightfulness”) of Yahweh. How would this desire be fulfilled? Well, he must ask God, of course; that He would graciously reveal Himself to him. But he must also seek Him for himself, by spending time in God’s word, and prayer, and personal worship. And this David did, as later in the Psalm he says that when God told him to seek His face, his response was “Thy face O Lord I shall seek”! (:8) Both of these elements were present in David’s search to know God: he both asked, and he actively sought.
If you have a particular desire or need at this time — whether it is knowing God, or building a ministry, or finding a job, or whatever it is — remember to apply BOTH necessary elements of the equation to your need: first ASK God for it, and then SEEK it with all your heart!