From "Manual of Muad'Dib" by the Princess Irulan

I had no choice but to do this , she thought. We must move swiftly if we're to secure our place among these Fremen .
Paul climbed to the ledge, leaving the children below. He stopped in front of his mother, glanced at Stilgar, back to Jessica. "What is happening? I thought I was being summoned to council."
Stilgar raised a hand for silence, gestured to his left where another way had been opened in the throng. Chani came down the lane opened there, her elfin face set in lines of grief. She had removed her stillsuit and wore a graceful blue wraparound that exposed her thin arms. Near the shoulder on her left arm, a green kerchief had been tied.
Green for mourning , Paul thought.
It was one of the customs the two sons of Jamis had explained to him by indirection, telling him they wore no green because they accepted him as guardian-father.
"Are you the Lisan al-Gaib?" they had asked. And Paul had sensed the jihad in their words, shrugged off the question with one of his own—learning then that Kaleff, the elder of the two, was ten, and the natural son of Geoff. Orlop, the younger, was eight, the natural son of Jamis.
It had been a strange day with these two standing guard over him because he asked it, keeping away the curious, allowing him the time to nurse his thoughts and prescient memories, to plan a way to prevent the jihad.
Now, standing beside his mother on the cavern ledge and looking out at the throng, he wondered if any plan could prevent the wild outpouring of fanatic legions.
Chani, nearing the ledge, was followed at a distance by four women carrying another woman in a litter.
Jessica ignored Chani's approach, focusing all her attention on the woman in the litter—a crone, a wrinkled and shriveled ancient thing in a black gown with hood thrown back to reveal the tight knot of gray hair and the stringy neck.
The litter-carriers deposited their burden gently on the ledge from below, and Chani helped the old woman to her feet.
So this is their Reverend Mother , Jessica thought.
The old woman leaned heavily on Chani as she hobbled toward Jessica, looking like a collection of sticks draped in the black robe. She stopped in front of Jessica, peered upward for a long moment before speaking in a husky whisper.
"So you're the one." The old head nodded once precariously on the thin neck. "The Shadout Mapes was right to pity you."
Jessica spoke quickly, scornfully: "I need no one's pity."
"That remains to be seen," husked the old woman. She turned with surprising quickness and faced the throng. "Tell them, Stilgar."
"Must I?" he asked.
"We are the people of Misr," the old woman rasped. "Since our Sunni ancestors fled from Nilotic al-Ourouba, we have known flight and death. The young go on that our people shall not die."
Stilgar took a deep breath, stepped forward two paces.
Jessica felt the hush come over the crowded cavern—some twenty thousand people now, standing silently, almost without movement. It made her feel suddenly small and filled with caution.
"Tonight we must leave this sietch that has sheltered us for so long and go south into the desert," Stilgar said. His voice boomed out across the uplifted faces, reverberating with the force given it by the acoustical horn behind the ledge.
Still the throng remained silent.
"The Reverend Mother tells me she cannot survive another hajra," Stilgar said. "We have lived before without a Reverend Mother, but it is not good for people to seek a new home in such straits."
Now, the throng stirred, rippling with whispers and currents of disquiet.
"That this may not come to pass," Stilgar said, "our new Sayyadina Jessica of the Weirding, has consented to enter the rite at this time. She will attempt to pass within that we not lose the strength of our Reverend Mother."
Jessica of the Weirding , Jessica thought. She saw Paul staring at her, his eyes filled with questions, but his mouth held silent by all the strangeness around them.