As stated on an earlier occasion,
The Bible speaks of those who are “blessed” or “happy”. What is it that makes someone able to receive such a designation? It is because they have taken hold of that which brings eternal satisfaction. What is it? David declared, “Blessed is the one you choose and bring near, to dwell in your courts! We shall be satisfied with the goodness of your house, the holiness of your temple!” (Psalm 65:4).
By means of God’s sovereign grace, true satisfaction can only be found in Him. Only in Him can we find forgiveness for all our sins (Psalm 32:1), only in Him can we possess lasting blessings (Eph. 1:3) and only in Him can we experience eternal pleasure (Psalm 16:11). Real happiness is found exclusively in the Lord God Almighty. “Oh, taste and see that the Lord is good! Blessed is the man who takes refuge in him!” (Psalm 34:8).
This leads us to Psalm 1.The kind of happiness described in this Psalm is not derived from human nature or accomplishment. What is the happiness in this psalm? “Blessed is the man” is a condition granted by God. They are in a state and position of Divine favour (cf. Psalm 65:4). In this Psalm we are shown two different ways of life with two different outcomes (1:6). We will see the way of the righteous (1:1-3) and the way of the wicked (1:4-6).
THE WAY OF THE RIGHTEOUS 1:1-3
In these verses we learn three things about the way of the righteous, (1) their rejection, (2) their responsibility and (3) their result.
Their Rejection (1:1). “Blessed is the man who walks not in the counsel of the ungodly, nor stands in the path of sinners, nor sits in the seat of the scornful” (Psalm 1:1). John Calvin summarizes this by saying, “the servant of God must endeavour utterly to abhor the life of ungodly men”. How is this done? By avoiding three things. First, the godly do not walk “in the counsel of the ungodly“. That is to say, they do not conduct their life according to the ideas and wisdom of the world. The godly heed the instruction, “Do not enter the path of the wicked, and do not walk in the way of evil. Avoid it, do not travel on it; turn away from it and pass on” (Prov. 4:14-15). The word ungodly refers to those that are not devoted to the Lord and have no regard for Him. Secondly, the godly does not stand in “the path of sinners“. That is, they do not partake of the activities of those who sin against the Lord. Finally, the godly does not sit in “the seat of the scornful“. To sit refers to being settled and comfortable with the “scornful“. These are those who opening speaking evil against the Lord.
Their Responsibility (1:2). In addition to rejecting that which is ungodly, the blessed man makes the Word of God his chief responsibility. The Psalm continues, “his delight is in the law of the Lord, and in His law he meditates day and night” (Psalm 1:2). Here we see two aspect of his responsibility, (1) attitude and (2) action. The word “delight” refers to taking pleasure in. To delight in the law of the Lord means to long for it and to treasure it. How do you gain such a desire? Know that it is food for the soul (Psalm 19:10) and light for our path (Psalm 119:105), then pray to the Lord to renew such a delight in us. He continues, “and in His law he meditates day and night“. This refers to going over and over what we read or remembered. Literally the word means to “muse” or “mutter”.
Their Result (1:3). Such actions provide the following result, “He shall be like a tree planted by the rivers of water, that brings forth its fruit in its season, whose leaf also shall not wither; and whatever he does shall prosper” (Psalm 1:3). The prosperity here needs to be understood as a soul prospering with eternal benefits (cf. Psalm 73:17).
THE WAY OF THE WICKED 1:4-6
In contrast to the way of the righteous, the final verses talk about the way of the wicked. Verse 4 begins by saying, “The ungodly are not so“. This provides a strong contrast to the way of the righteous. Instead of being firmly planted, they are liked to “the chaff which the wind drives away“. They are likened to the husk – the dry outer coating of grain. Once it is separated from the grain and thrown into the air it is blown away by the wind. It is for this reason that despite the apparent success and prospering of the wicked, their way will come to ruin. The Psalm continues, “Therefore the ungodly shall not stand in the judgment, nor sinners in the congregation of the righteous” (Psalm 1:5). The Psalm ends by saying, “For the Lord knows the way of the righteous, but the way of the ungodly shall perish” (Psalm 1:6). The Lord is intimately acquainted with all that goes on in the life of His people, and the way of the wicked will one day end.
 Calvin, John. Calvin’s Commentaries, Volume IV, 3