Corollary 9.2.9.9. Let $\operatorname{\mathcal{C}}$ be an $\infty $-category and let $(S_ L, S_ R)$ be a factorization system on $\operatorname{\mathcal{C}}$. Then $(S_ L, S_ R)$ is a weak factorization system on $\operatorname{\mathcal{C}}$.

$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$

**Proof.**
The only nontrivial point is to verify that $S_{L}$ and $S_{R}$ are closed under retracts, which follows from Corollary 9.2.9.8.
$\square$