Supernatural Rarepair Shipfest 2013

Castiel is still getting used to his relationship with Sam. After Dean casually mentions that the worst thing you can do is bring the "L word" up, Castiel is worried that telling Sam he loves him will freak the hunter out and ruin what they have. So he says it in Enochian instead, having it slip out when they're alone. Sam doesn't know exactly what Castiel's saying but he can tell just by the tender look in his eyes.