Psalm 95

1 Oh come, let us sing to the Lord;
    let us make a joyful noise to the rock of our salvation!
2 Let us come into his presence with thanksgiving;
    let us make a joyful noise to him with songs of praise!
3 For the Lord is a great God,
    and a great King above all gods.
4 In his hand are the depths of the earth;
    the heights of the mountains are his also.
5 The sea is his, for he made it,
    and his hands formed the dry land.
6 Oh come, let us worship and bow down;
    let us kneel before the Lord, our Maker!
7 For he is our God,
    and we are the people of his pasture,
    and the sheep of his hand.
Today, if you hear his voice,
8  do not harden your hearts, as at Meribah,
    as on the day at Massah in the wilderness,
9  when your fathers put me to the test
    and put me to the proof, though they had seen my work.
10 For forty years I loathed that generation
    and said, “They are a people who go astray in their heart,
    and they have not known my ways.”
11 Therefore I swore in my wrath,
    “They shall not enter my rest.”

I might categorize Psalm 95 as a feel-good psalm if it ended with the first part of verse 7.

It is a great call to worship God.

 1 Oh come, let us sing to the Lord;
    let us make a joyful noise to the rock of our salvation!
2 Let us come into his presence with thanksgiving;
    let us make a joyful noise to him with songs of praise!
3 For the Lord is a great God,
    and a great King above all gods.
4 In his hand are the depths of the earth;
    the heights of the mountains are his also.
5 The sea is his, for he made it,
    and his hands formed the dry land.
6 Oh come, let us worship and bow down;
    let us kneel before the Lord, our Maker!
7 For he is our God,
    and we are the people of his pasture,
    and the sheep of his hand.

But then comes a warning at the end of verse 7:

Today, if you hear his voice,
do not harden your hearts, as at Meribah,
as on the day at Massah in the wilderness,
when your fathers put me to the test
and put me to the proof, though they had seen my work.

What is going on here?

A good reference Bible will point you to Exodus 17, the story where the people of Israel complain (again), and God tells Moses the strike the rock at Horeb and water will come out of it. Moses does this, and God provides water. Exodus 17:7 says:

And he called the name of the place Massah and Meribah, because of the quarreling of the people of Israel, and because they tested the Lord by saying, “Is the Lord among us or not?”

Massah means testing. Meribah means quarreling.

In v. 7-9 God is the one who reminds the worshipping community, amid their joyous worship, of their past when they tested God and quarreled with the Lord in the wilderness. The warning is jarring and stern:

For forty years I loathed that generation
and said, “They are a people who go astray in their heart,
and they have not known my ways.”
Therefore I swore in my wrath,
“They shall not enter my rest.” (v. 10-11)

And there the Psalm ends.

Beth Tanner provides insight:

We can make God so angry that worship is an abomination (Amos 5:18-25). This is not a nice word to hear, but it is true. This psalm leaves people who are anticipating a festival, and indeed whose festival had already begun with the shouts in vv. 1-2, on their knees contemplating the sins of past generations that serve as a warning to them. “Is the praise honest and real?” is the question this psalm asks as the party begins. “Do you really know what you are doing?” “Are you really prepared to encounter God’s face?” The questions for these ancient ones should also be ours. Worship, full-voiced praise-filled worship, requires an understanding of the serious nature of that praise, for as one encounters all of these enthronement songs, God is praised for being the Judge and Controller of the creation and all the peoples. The praise of God cannot be taken lightly, and so the congregation is left here on their knees to understand just that.