Learn Hardcore German: Ich wasche mir die Hände mit Seife.

In German reflexive constructions, if you wash your whole self, the reflexive pronoun is the direct object (accusative): Ich wasche mich. But when you wash a specific body part, that part becomes the direct object (here die Hände = accusative), so the reflexive pronoun shifts to the indirect object (dative): mir.

Why say die Hände and not meine Hände?

The reflexive pronoun mir already indicates that it’s your own hands. Adding meine Hände would be redundant. German normally uses the definite article with body parts in reflexive actions: Ich wasche mir die Hände, not meine Hände.

What case is die Hände in, and why?

Die Hände is in the accusative plural. The verb waschen is transitive and takes a direct object; here that object is die Hände (your hands), so it appears in the accusative case.

Could I drop mir and simply say Ich wasche die Hände mit Seife? Would that be correct?

You could say Ich wasche die Hände mit Seife, but it sounds less natural in German and leaves open whose hands you’re washing. Including mir clarifies that you’re washing your own hands.

Why is it mit Seife and not mit der Seife, and why does mit require the dative case?

The preposition mit always governs the dative. When you speak of a substance or material in a general sense (soap in general), German usually drops the article: mit Seife (“with soap”). If you refer to one specific soap bar, you could say mit der Seife.

Why does the dative pronoun mir come before the accusative noun die Hände?

Word‑order rule: pronouns precede nouns. Also when both objects are nouns, dative traditionally comes before accusative. Here mir (pronoun, dative) goes before die Hände (noun, accusative).

Is waschen a reflexive verb here, and how do I choose between mich/mir, dich/dir, etc.?

Waschen is not inherently reflexive but can be used reflexively when you wash yourself or a body part. If the action’s direct object is yourself, use the accusative reflexive pronoun (mich, dich, sich, etc.). If you wash a part of yourself, that part is accusative and the reflexive pronoun becomes dative (mir, dir, sich, etc.).

How would I form the question “Are you washing your hands with soap?” and why does the verb change?

You invert subject and verb: Waschst du dir die Hände mit Seife? Note that in the du‑form waschen undergoes the vowel change a → ä (“du wäschst”). In the ich‑form there is no change, so it remains ich wasche.