Psa 106:28-29
They joined themselves also to Baal-peor,
And ate sacrifices offered to the dead.
Thus they provoked Him to anger with their deeds,
And the plague broke out among them.

They worshipped pagan gods - Baal-peor is an example.
They ate food sacrificed to pagan gods.
They provoked the Lord to anger due to this.
The Lord sent a plague among them.

Here is a quick synopsis of the event…

Num 25:1-3, 5
While Israel remained at Shittim, the people began to play the harlot with the daughters of Moab.
For they invited the people to the sacrifices of their gods, and the people ate and bowed down to their gods.
So Israel joined themselves to Baal of Peor, and the LORD was angry against Israel.
So Moses said to the judges of Israel, “Each of you slay his men who have joined themselves to Baal of Peor.”

Num 31:16
“Behold, these caused the sons of Israel, through the counsel of Balaam, to trespass against the LORD in the matter of Peor, so the plague was among the congregation of the LORD.

Deu 4:3
“Your eyes have seen what the LORD has done in the case of Baal-peor, for all the men who followed Baal-peor, the LORD your God has destroyed them from among you.

Deu 32:17
“They sacrificed to demons who were not God,
To gods whom they have not known,
New gods who came lately,
Whom your fathers did not dread.

Jos 22:17
‘Is not the iniquity of Peor enough for us, from which we have not cleansed ourselves to this day, although a plague came on the congregation of the LORD,

Hos 9:10
I found Israel like grapes in the wilderness;
I saw your forefathers as the earliest fruit on the fig tree in its first season.
But they came to Baal-peor and devoted themselves to shame,
And they became as detestable as that which they loved.

They sacrificed to demons.
They received the counsel of Balaam.

So, what does this have to do with us today.

Rare is the week that passes that I do not hear doctrine of demons communicated as “truth”.
False gospel is rampant.

Most of this is due to ignorance and lack of knowledge of the Word and the desire to tickle the ears of man.

Such is not a surprise.
We have been forewarned.

1Ti 4:1-2
But the Spirit explicitly says that in later times some will fall away from the faith, paying attention to deceitful spirits and doctrines of demons,
by means of the hypocrisy of liars seared in their own conscience as with a branding iron,

2Ti 4:3-4
For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears;
And they shall turn away their ears from the truth, and shall be turned unto fables.

Do not join with doctrine of demons.

Walk in the Spirit.
Know the Word.