This is a deleted Jalec scene from City of Glass, where Jace kisses Alec to convince him that he’s not really in love with him.
“Drop it, Jace,” Alec said in a warning tone.
Jace was having none of being warned. “Magnus says it’s because you’re hung up on me. Is that true?”
There was a moment of utter silence. Then Alec gave a despairing howl of horror and put his hands up to cover his face. “I am going to kill Magnus. Kill him dead.”
“Don’t. He cares about you. He really does. I believe that,” Jace said, managing to sound only a little bit awkward. “Look. I don’t want to push you into anything, but do you maybe want to —”
“Call Magnus? Look, that’s a dead end, I know you’re trying to be helpful, but —”
“—kiss me?” Jace finished.
Alec looked as if he were about to fall off his chair. “WHAT? What? What?”
“One what would do.” Jace did his best to look as if this were the sort of suggestion one made all the time. “I think it might help.”
Alec looked at him with something like horror. “You don’t mean that.”
“Why wouldn’t I mean it?”
“Because you’re the straightest person I know. Possibly the straightest person in the world.”
“Exactly,” Jace said, and leaned forward, and kissed Alec on the mouth.
The kiss lasted approximately four seconds before Alec pulled forcefully away, throwing his hands up as if to ward Jace off from coming at him again. He looked as if he were about to throw up. “By the Angel,” he said. “Don’t ever do that again.”
“Oh yeah?” Jace grinned, and almost meant it. “That bad?”
“Like kissing my brother,” said Alec, with a look of horror in his eyes.
“I thought you might feel that way.” Jace crossed his arms over his chest. “Also, I’m hoping we can just gloss over all the irony here in what you just said.”
“We can gloss over whatever you want to,” Alec said fervently. “Just don’t kiss me again.”