To do Your will
In psalm 39 (40 in Hebrew) one finds….
“Sacrifice and offering you did not desire, you have opened my ears: burnt offering and sin offering you did not required, then said I: “ Lord I am coming, in the volume of the book it is written of me, I delight to do your will O my God, your law is in my heart” psalm 39, 7-9
corps et âme Psalm 39 is first a claim of hope by a poor man: “ I was full of hope in the Lord, He looked at me, He listened to my voice”. God gives a sign to show that he heard indeed who prayed to him “He opened his ears” to words that fill him with joy. Just like a deaf person suddenly healed discovers the marvellous world of sounds. The psalmist is receiving the revelation of a message of liberation: this time I understood, I got it!
What did he understand? Simply what he had heard so often from the prophets: it is not important to go to the temple to present offerings of beef or lamb if these offerings do not express a personal move and a deep feeling to imitate the Holy God to whom we are addressing.  
The essential part is written in the Holy Book that Jesus himself will summarize as follow: “ You will love God with all your heart …and your neighbour like yourself”. It is what the psalmist call “ to do your wills” a plural referring to some important parts of the Bible where God is giving his will. A particular case is the Decalogue: a collection of ten commandments to be alive, bringing joy, even if they are written in negative sentences that seems to set a primary sense of prohibition: ‘Thou shall not kill”, “Thou shall not steal…”
rouleau du livre
In reading this psalm as a prayer, Jesus of Nazareth certainly envisaged the positive and joyful aspect “ of doing his will; He will put these words in the prayer of Our Father “ That will be done on earth as it is in heaven”, because to do God’s will is already to put a piece of heaven into our life. The psalmist does not speak about the Law as a constraint or a boring obligation. Too often, the Law is seen like a list of arid things to do or not to do; an abstract code, without life.  
faire ta volonté For the psalmist, to love God and his neighbour is nothing afflicting or sad; it is a pleasant course, full of rewards and joy, a deep pleasure: “I take my pleasure in your Law, in the depth of my heart” It is not simply a spiritual joy but a material joy.
In fact, in the Greek translation of the Bible, it is pointed out: “ You did not want offerings, … you gave me a body… and I took pleasure in your Law” A rewarding pleasure, including both body and soul.  
We are far away from a status of a slave, showing a miserable face that is a caricature of a believer. Serving God is different from doing “His wills” as for a despotic master. Such an image of God would not honour Him. We will follow much willingly a God from the beatitudes who puts his pleasure in making us happy and in helping us.
In a monastery parlour of the Visitation in the French city of Moulins, one can see, written in large letters, this recommendation from Saint Jeanne de Chantal: “ Love God with all your heart and experiment the happiness to belong to him, it is worth more than a thousand worlds”