Devarim 13:13-17 (12-16)
13 (12) Ki-tishma be’achat areycha, asher YHVH Eloheycha noten lecha lashevet sham -- lemor.
If you should hear concerning one of your cities, which YHVH your Elohim has given you to dwell there, saying:
14 (13)Yatse’u anashim b’ney-V’liya’al, mikirbecha, vayadichu et-yoshvey iram, lemor: nelchah, vena’avdah elohim acherim -- asher lo-yedatem.
"The sons of Beliya'al have gone forth among you, and has drawn away the inhabitants of their city, saying: 'Let's go about and serve other elohim, which you have not known.'"
15 (14) Vedarashta vechakarta vesha’alta, heytev; vehineh emet nachon hadavar, ne’estah hato’evah hazot bekirbecha.
You shall then inquire and and examine carefully and ask thoroughly, and behold, if the matter is true and certain, that such an abomination was done among you,
16 (15) Hakeh takeh, et-yoshvey ha’ir hahi — lefi-charev: hacharem otah ve’et-kol-asher-bah ve’et-behemtah, lefi-charev.
Striking, you shall strike, the inhabitants of that city, by the sword; destroy it completely all within it, and the cattle, by the sword.
17 (16) Ve’et-kol-shlalah, tikbots el-toch rechovah, vesarafta va’esh et-ha’ir ve’et-kol-shlalah kalil l’YHVH Eloheycha; vehayetah tel olam; lo tibaneh od.
And all the spoil, you shall gather in the midst of the open square, and burn with fire the city and all the spoil entirely, like the burnt offering unto YHVH, and it shall be a mound of ruins forever, it shall never be rebuilt.

This mitzvah relates to the Land (Eretz Yisra'el), for it refers to the cities that YHVH has given them to dwell there. Eretz Yisra'el is the special inheritance of the children of Avraham.

They would not allow for any Jewish city in Yisra'el willfully disregard the mitzvot relating to idolatry. The city could promote the spread of idolatry to other parts of Eretz Yisra'el; therefore it had to be destroyed.

After the conquest of Kena'an, it was rumored that the tribes of Gad and Re'uven had built an altar other than the one that is the Tabernacle. The Torah said that there was only one place for sacrifice, the place that YHVH had chosen. The rest of Yisra'el was concerned. They prepared for war against these tribes. They asked the tribes why there rebelling against YHVH. The tribes of Gad and Re'uven insisted that the altar was not for sacrifice, but as a witness.

The Mighty One, Elohim, YHVH, the Mighty One, Elohim, YHVH, he knows; and Yisra’el he shall know: if it be in rebellion, or if in trespass against YHVH (don’t save us this day), that we have built us an altar to turn away from following YHVH; or if to offer thereon burnt offering or meal offering, or if to offer sacrifices of shalom offerings thereon, let YHVH himself require it; And if we have not rather out of carefulness done this, and of purpose, saying, In time to come your children might speak to our children, saying, What have you to do with YHVH, the Elohim of Yisra’el? For YHVH has made the Yarden a border between us and you, you children of Re’uven and children of Gad; you have no portion in YHVH: so might your children make our children cease from fearing YHVH. Therefore we said, Let us now prepare to build us an altar, not for burnt offering, nor for sacrifice: but it shall be a witness between us and you, and between our generations after us, that we may do the service of YHVH before him with our burnt offerings, and with our sacrifices, and with our shalom offerings; that your children may not tell our children in time to come, You have no portion in YHVH. Therefore said we, It shall be, when they so tell us or to our generations in time to come, that we shall say, Behold the pattern of the altar of YHVH, which our fathers made, not for burnt offering, nor for sacrifice; but it is a witness between us and you. Far be it from us that we should rebel against YHVH, and turn away this day from following YHVH, to build an altar for burnt offering, for meal offering, or for sacrifice, besides the altar of YHVH our Elohim that is before his tent. Pinechas the son of El‘azar the kohen and the princes, returned from the children of Re’uven, and from the children of Gad, out of the land of Gil‘ad, to the land of Kena‘an, to the children of Yisra’el, and brought them word again. The thing pleased the children of Yisra’el; and the children of Yisra’el blessed Elohim and spoke no more of going up against them to war, to destroy the land in which the children of Re’uven and the children of Gad lived. (Yehoshua 22:22-33)

They were prepared to go against the tribes of Gad and Re'uven for what appeared to idolatry.

The people who motivate the people to idolatry are called B'nei Beliya'al. Beliya'al means without benefit. It is basically saying that these were good for nothing people. 2 Corinthians 6:14-15
Do not yoke yourselves together in a team with unbelievers. For how can righteousness and lawlessness be partners? What fellowship does light have with darkness? What harmony can there be between the Messiah and Beliya‘al? What does a believer have in common with an unbeliever?

This passage connects Beliya'al with lawlessness and darkness, as opposed to righteousness, light and the Messiah. The Talmud Sanhedrin 111b refers to them as men without discipline. The Syriac translates the word as satan. The connection with Beliya'al and hasatan is also made in Book of Jubiless 1:20.

The judges of the people were to make careful inquiry of at least two witnesses (Talmud Sanhedrin 40b).

Devarim (Deuteronomy) 19:15
One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sins: at the mouth of two witnesses, or at the mouth of three witnesses, shall a matter be established.

Revelation 21:8
But as for the cowardly, the untrustworthy, the vile, the murderers, the sexually immoral, those who misuse drugs in connection with the occult, idol-worshippers, and all liars—their destiny is the lake burning with fire and sulphur, the second death."

YHVH will abolish all idolatry forever. The punishment is fire, the same punishment in this mitzvah.

What is the principal of this mitzvah? How can we apply it to our lives? We should get rid of anything that relates to idolatry, anything that takes us away from a pure relationship with YHVH. It is not just a matter of just throwing it away, but it must be completely destroyed so that others may not be enticed by it.