大乘起信論義記 3.471

3.471

謂四禪四空等世間諸定及不淨安般等，但取境相定，皆名世間定也，以味著定境故，不離於我，故云與外道共。共者同得此事定故。以其共故，若得善友護助之力，或可得入佛法；若離善友，則入邪道也。

This means that the worldly samādhis such as the four dhyānas and four formless attainments, as well as [contemplations of] impurity, ānāpāna, and the like—all samādhis that merely grasp phenomenal marks—are named worldly samādhi. Because one relishes and clings to the realm of samādhi, one is not separated from self; hence it says, 'shared with non-Buddhists.' 'Shared' means that they equally attain this phenomenal samādhi. Because they are shared, if one obtains the protective and assisting power of a good spiritual friend, one may perhaps enter the Buddha-Dharma; if separated from a good friend, one enters heterodox paths.