The spell Holy Weapon empower a "weapon you touch" to do extra damage (2d8 radaint per hit) and shed light (30 feet bright light, 30 feet dim light). It has one final feature (XGtE, p. 157, bold added):
As a bonus action on your turn, you can dismiss this spell and cause the weapon to emit a burst of radiance. Each creature of your choice that you can see within 30 feet of you must make a Constitution saving throw. On a failed save, a creature takes 4d8 radiant damage, and it is blinded for 1 minute.
Now, note that unlike some spells (like Shillelagh), this spell doesn't end if you are no longer touching the weapon you cast it upon. So you could conceivably cast this spell on an ally's weapon (say, if you're a cleric and you have a fighter ally who attacks many times in one turn). If you did this, I found myself wondering where the "burst of radiance" would be centered: on the spellcaster, or on the weapon?
In seemed unambiguous at first, since every time a spell mentions "you", it's referring to the caster. But at the same time, the spell says that the burst of radiance comes from the weapon, so I became unsure.
So how would you rule this? If the person who casts Holy Weapon is far away from the weapon when they activate the "burst of radiance" where is the burst centered? On the spellcaster, or on the weapon?
Best Answer
The spell has been Errata'd to make the weapon the source of the damage + blindness
I'm leaving the below answer as-is for reference, but as of April 2020, official errata for Xanathar's Guide to Everything has indeed made the exact change I advocated below.
The RAI (and revised RAW) is that the Weapon is the origin of the Damage + Blindness, not the Spellcaster
Jeremy Crawford has confirmed that the text in Holy Weapon is a mistake, and would be corrected in future printings:
I don't know if the revised version has already been printed, or if Errata has been released, or what the revised wording will look like. I predict, however, it'll probably be something like this: