Part of the answer to this question what can a wizard do without a spellbook got me wondering. It states that you, as a wizard, can't cast a ritual spell without your spellbook.
And I can't help question whether that is true?
Because the rules doesn't actually seem to state that explicitly.
Let's look at the rules for rituals in the PHB.
The caster must also have the spell prepared or on his or hers list of spells known, unless the character's ritual feature specifies otherwise, as the wizard does.
So while those rules doesn't require a spellbook, they do single out the wizard's ritual feature.
So what does the wizard ritual feature say?
PHB pg. 114
You can cast a wizard spell as a ritual if that spell has the ritual tag and you have the spell in your spellbook. You don't need to have the spell prepared
Now while the rules mention a spellbook, they don't actually state that you need to use it during the ritual casting. Just that the spell already needs to be inscribed in the spellbook. Like how the general rules for rituals state that a spell needs to be on the caster's list of known spells.
And if you look at the wording, it it is very similar to other wizard features that require you to have the spell in your spellbook but doesn't require you to access your spellbook while casting.
For example, the Spell Mastery feature:
PHB. pg. 115.
Choose a 1st-level wizard spell and a 2nd-level wizard spell that are in your spellbook. You can cast those spells at their lowest level without expending a spell slot when you have them prepared.
or the Signature spell feature:
PHB: pg. 115.
Choose two 3rd-level spells in your spellbook as your signature spells.
In both examples the rules seem to treat the spellbook as a reference to the spells known by the wizard, identically to the known spell list other caster classes use. And not as a physical thing the wizard is actually accessing at that moment to use those features.
Then compare it to the Arcane Recovery feature that explicitly states that you need to be using the spellbook for that feature to work.
PHB. pg. 115
You have learned to regain some of your magical energy by studying your spellbook.
There the rule explicitly states that the wizard must be using ("studying") the actual physical spellbook for the feature to work.
So by comparing the RAW for rituals in general and the different wizard features there doesn't seem to be anything that says that a wizard needs to be using the actual physical spellbook while casting a spell as a ritual. And while, from a certain logical and thematic viewpoint, it makes sense for a wizard to read from the spellbook while performing a ritual, nothing in the RAW seem to require it.
So can a Wizard cast a spell as a ritual without physically accessing a spellbook? And is there an official ruling, either way?