simp[←Rew.hom_comp_app]
L : Language
Δ Δ₁ Δ₂ Γ : Sequent L
p✝ q r : SyntacticFormula L
f : ℕ → SyntacticTerm L
p : SyntacticSemiformula L 1
⊢ (Rew.hom Rew.free) ((Rew.rewrite fun x => Rew.bShift (f x)).hom p) =
    (Rew.rewrite (&0 :>ₙ fun x => ⇑ (f x))).hom ((Rew.hom Rew.free) p)
L : Language
Δ Δ₁ Δ₂ Γ : Sequent L
p✝ q r : SyntacticFormula L
f : ℕ → SyntacticTerm L
p : SyntacticSemiformula L 1
⊢ (Rew.comp Rew.free (Rew.rewrite fun x => Rew.bShift (f x))).hom p =
    ((Rew.rewrite (&0 :>ₙ fun x => ⇑ (f x))).comp Rew.free).hom p