Starý nápis

The image shows a wall inscription in Cuandixia Village, a historic Ming-era settlement in Beijing’s Mentougou District.

The four large Chinese characters on the wall are: 佛通德恒

These characters, read from right to left in traditional Chinese calligraphic style, are:
恒 (héng) — constant, enduring
德 (dé) — virtue, moral character
通 (tōng) — to connect, to communicate, to be open
佛 (fó) — Buddha, Buddhism

This phrase can be interpreted as "Buddha's virtue is constant" or "Buddhist virtue endures."