he hated seeing Alastor getting close to you, he hated Al in geniral, so when he saw him put an arm around your shoulder, he nearly snapped... Al knew how he felt about you, and how close you two were, and so he wanted to get a rise out of him by getting close to you, he stared daggers at Al, gripping the staff in his hand and making Al smirk at his reaction as Lucifer mumbled to himself, his jealousy boiling over

"Oh, hell no... you're not taking her from me..."