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

If I die in the attempt, what will become of him? Jessica asked herself. Again she felt the misgivings fill her mind.
Chani led the old Reverend Mother to a rock bench deep in the acoustical horn, returned to stand beside Stilgar.
"That we may not lose all if Jessica of the Weirding should fail," Stilgar said, "Chani, daughter of Liet, will be consecrated in the Sayyadina at this time." He stepped one pace to the side.
From deep in the acoustical horn, the old woman's voice came out to them, an amplified whisper, harsh and penetrating: "Chani has returned from her hajra—Chani has seen the waters."
A sussurant response arose from the crowd: "She has seen the waters."
"I consecrate the daughter of Liet in the Sayyadina," husked the old woman.
"She is accepted," the crowd responded.
Paul barely heard the ceremony, his attention still centered on what had been said of his mother.
If she should fail?
He turned and looked back at the one they called Reverend Mother, studying the dried crone features, the fathomless blue fixation of her eyes. She looked as though a breeze would blow her away, yet there was that about her which suggested she might stand untouched in the path of a coriolis storm. She carried the same aura of power that he remembered from the Reverend Mother Gaius Helen Mohiam who had tested him with agony in the way of the gom jabbar.
"I, the Reverend Mother Ramallo, whose voice speaks as a multitude, say this to you," the old woman said. "It is fitting that Chani enter the Sayyadina."
"It is fitting," the crowd responded.
The old woman nodded, whispered: "I give her the silver skies, the golden desert and its shining rocks, the green fields that will be. I give these to Sayyadina Chani. And lest she forget that she's servant of us all, to her fall the menial tasks in this Ceremony of the Seed. Let it be as Shai-hulud will have it." She lifted a brown-stick arm, dropped it.
Jessica, feeling the ceremony close around her with a current that swept her beyond all turning back, glanced once at Paul's question filled face, then prepared herself for the ordeal.
"Let the watermasters come forward," Chani said with only the slightest quaver of uncertainty in her girl-child voice.
Now, Jessica felt herself at the focus of danger, knowing its presence in the watchfulness of the throng, in the silence.
A band of men made its way through a serpentine path opened in the crowd, moving up from the back in pairs. Each pair carried a small skin sack, perhaps twice the size of a human head. The sacks sloshed heavily.
The two leaders deposited their load at Chani's feet on the ledge and stepped back.
Jessica looked at the sack, then at the men. They had their hoods thrown back, exposing long hair tied in a roll at the base of the neck. The black pits of their eyes stared back at her without wavering.
A furry redolence of cinnamon arose from the sack, wafted across Jessica. The spice? she wondered.
"Is there water?" Chani asked.
The watermaster on the left, a man with a purple scar line across the bridge of his nose, nodded once. "There is water, Sayyadina," he said, "but we cannot drink of it."
"Is there seed?" Chani asked.
"There is seed," the man said.
Chani knelt and put her hands to the sloshing sack. "Blessed is the water and its seed."
There was familiarity to the rite, and Jessica looked back at the Reverend Mother Ramallo. The old woman's eyes were closed and she sat hunched over as though asleep.
"Sayyadina Jessica," Chani said.
Jessica turned to see the girl staring up at her.
"Have you tasted the blessed water?" Chani asked.
Before Jessica could answer, Chani said: "It is not possible that you have tasted the blessed water. You are outworlder and unprivileged."
A sigh passed through the crowd, a sussuration of robes that made the nape hairs creep on Jessica's neck.
"The crop was large and the maker has been destroyed," Chani said. She began unfastening a coiled spout fixed to the top of the sloshing sack.
Now, Jessica felt the sense of danger boiling around her. She glanced at Paul, saw that he was caught up in the mystery of the ritual and had eyes only for Chani.