The Avnei Nezer teaches: When one only speaks Torah and mitzvos, and doesn’t profane his mouth with forbidden speech, his mouth becomes like a kli shares, the utensils of the Beis HaMikdash.

One of the features of the keilim of the Beis HaMikdash is that when items are placed inside them, they become holy.

Similarly, due to the holiness of his mouth, his tefillos will be holy and take on a much stronger effect. All his prayers will be answered.

~ R’ Elimelech Biderman