Is it obligatory for a handsome, beardless person to delete his pictures from Facebook if he fears they might cause temptation, or is it merely recommended and preferable for him to do so?

Allah commanded the lowering of the gaze from whatever incites temptation and lust and leads to forbidden acts. Allah Almighty says: (Tell the believing men to lower their gaze and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do. And tell the believing women to lower their gaze and guard their private parts) An-Nur/30-31. The sight is the greatest gate to the heart. It is impermissible to look at a handsome beardless youth by agreement of the scholars if it is with lust or fear of temptation. However, without lust and with safety from temptation, there is no harm. It is forbidden to publish pictures of those from whom temptation is feared, as a pre-emptive measure against temptation and corruption.