A little more information on the phrase that is commonly found in Gatha as "together with all sentient beings" or "l vow with/for all beings" or "may all living beings" or the like (当願衆生). This is a vital, really indispensable phrase in Gatha.
The reason is to dedicate the merit to other sentient beings, hoping that they will gain insight and liberation from the doing of such acts. By doing so, a seeming neutral act which is neither particularly positive or negative in Karmic effect (such as sleeping, washing the face, drinking tea, unlike a particularly hateful or angry act, for example) is turned into a positive action because of that concern for the well-being of others. Suddenly, one is not merely drinking tea for oneself, but for all beings, and thus the good Karma happens.
Most of our actions during the day are neutral or rather ignored and unnoticed as anything special, so the dedication within the Gatha creates a positive nature to the act, and the Gatha itself helps us notice how wondrous it is even to engage in the most ordinary behavior in our day. lt also reminds us that we are --never-- practicing simply for ourselves, but rather, for the benefit of all sentient being whom we have vowed to rescue and liberate in our Bodhisattva Vows.
Gassho, J
STLah