For Obi-Wan, it was love.
After being ignored and rejected all his life, simply the reassurance that he was loved was enough to soothe him. Qui-Gon would find him hidden away in the Temple Gardens, curled up under in the branches of the tallest tree he could climb, hoping to conceal himself amongst the leaves. When the elder Jedi approached, Obi-Wan wouldn't move or even look at his Master, refusing to admit his weakness even as the tears streamed down his cheeks.
He tried his best to hide the pain, afraid of being rejected from the only home he'd ever known. Afraid that if he screwed up just a little, they wouldn't want him any longer. But when Qui-Gon found him, all he had to do was say, "I love you my padawan. I'm here. It's going to be okay."
And Obi-Wan would fall into his arms and let the tears fall, holding tight to the one person who truly loved him.
"I will always be here for you, Obi-Wan."
For Anakin, it was hush.
When his emotions overwhelmed him, Anakin needed the world to be quiet. Anger, hurt, frustration- it would swirl within him, living inside his head without the decency of paying rent. The intrusive thoughts and nightmares became so loud that he couldn't find his center through the Force, couldn't even sleep from the overstimulation. It drove him mad, as it would any man, and it took everything he had not to scream; he would bite his tongue in a desperate fight to keep everything contained.
But Obi-Wan would hear him. When it all became too much, Obi-Wan would hear his tantrums, walk into his room, and take him by the hands. At first, the boy would struggle and try to escape, protesting, begging to be left alone.
But Obi-Wan would simply hold him tighter and whisper. "Hush, Anakin. Just relax. Breathe."
And Anakin would stop fighting. He would listen. He would breathe and give everything over to the one person who could take away the pain and make the world be quiet, if only for a moment.
"I will never abandon you, Anakin."
For Ahsoka, it was safe.
Ahsoka's world was harsh and cruel, all rough edges and unwelcome lessons. She'd tried so hard to prove she wasn't a little kid anymore only to be thrown into a war and forced to grow up far too quickly. Some days her vision would blur around the edges, blocking out the suffering around her so she could focus on staying alive, on taking another step forward, on the next breath.
On those days, when the nightmares came and the scars could not simply be soothed by bacta, a gentle hand always helped her heal. Anakin would find her sitting by herself, tucked into the smallest space imaginable, trying to shake off the horrors that she witnessed day in and day out.
After he coaxed her out, Anakin would knead the stress from her shoulders with one hand, before wrapping the other arm around her slight frame. "Just let go Snips. Don't be afraid. You're safe with me."
And Ahsoka could let go, allowing herself to be vulnerable and scared and a child, if only for a little while. She could, because she knew that the person she trusted the most would never see her as weak or incapable. That he understood.
"I will always protect you, Ahsoka."