They were plotting to kidnap these kids again — and vowed to fight their mom “to the death” to get them.

Even from jail, members of the Guatemala-based extremist Jewish cult “Lev Tahor” were planning the re-abduction of two Orthodox children — kids whose mother has now three times rescued from the group, according to a chilling new indictment obtained by The Post.

In threatening to seize the children back, the sick sect’s “boss” in Guatemala, speaking by phone in Yiddish, “used violent language” toward mom Sara Helbrans, the indictment alleges, “including that he will fight the mother until the last drop of blood and that they will fight her to the death.”

“I will take them out from under your hands,” the “boss” warned the mom of her children, Yante, 14, and Chaim, 12 — during a call she secretly recorded for the feds, the indictment said.

“And will take them back to their [cult member] father, with God’s help,” the unnamed leader allegedly threatened in the phone call.

Lev Tahor members were especially hell-bent on re-capturing the older child, Yante, so that the girl couldn’t testify against the cult, according to the indictment, which was filed this week in White Plains and charges alleged cult member Matityae Moshe Malka with conspiracy.

Cult members also wanted the girl reunited with her adult “husband,” accused cult member Jacob Rosner, according to the indictment.

Yante “is considered within Lev Tahor to be the wife of Jacob Rosner,” the Malka indictment alleges.

Malka is accused in Manhattan federal court of allegedly delivering cellphones to the girl in Brooklyn several times this month, so that cult leaders — including Sara’s brother, Nachman, who is incarcerated in Westchester County Jail — could talk secretly to her about her recapture, the indictment alleges.

Yante and Chaim are the grandchildren of the cult’s late founder, Shlomo Helbrans, who started the ultra-Orthodox sect in Israel in 1987.

In the years since then, he hopscotched the group around the world — to Brooklyn, Israel, Canada, Mexico and now Guatemala — often one step ahead of child welfare officials appalled by the group’s abusive living conditions.

Sara, who as Shlomo’s daughter had been raised in the cult, courageously escaped her cult-member husband with her children in November 2018 after learning that the 14-year-old was to be married to a cult elder.

Sara saved her children a second time after they were kidnapped back into the cult on Dec. 8, while the family was staying at a home in Woodridge, Sullivan County.

With the mom’s help, law enforcement recovered Yante and Chaim in Mexico on Dec. 27.

Five alleged cult members, including Malka, were taken into custody and deported to the US at that time, and the children were returned to their mother in New York, the indictment says.

Then, this month, the mother found that the cult was still communicating with Yante — through a series of cellphones smuggled to the child during multiple in-person visits by Malka, as the latest the indictment alleges.

Malka is one of five alleged cult members arrested in the kidnap plot; the others are Nachman Helbrans, Sara’s brother, and Jacob, Mayer and Aron Rosner.

Aron Rosner was released in January on $10 million bail in White Plains, where prosecutors alleged he was the group’s money man.

The lawyer who represented Malka at his first court appearance, in White Plains on March 26, did not respond to multiple requests for comment.