Let $H = \langle X \rangle$ then $H' = \langle [x_1, x_2]^h \mid x_1, x_2 \in X, h \in H \rangle$

Question

Let $H = \langle X \rangle$, then $$H' = \langle [x_1, x_2]^h \mid x_1, x_2 \in X, h \in H \rangle.$$

Obviously $$\langle [x_1, x_2]^h \mid x_1, x_2 \in X, h \in H \rangle \leq H'.$$ Any tips on how to proceed are greatly appreciated.