Jamieson, Fausset and Brown on Isaiah 56:2

2. (Lu 12:43).

the man--Hebrew, enosh, "a man in humble life," in contradistinction to Hebrew, ish, "one of high rank." Even the humblest, as "the stranger" and "the eunuch" (Is 56:4, 6), are admissible to these privileges.

this ... it--what follows: "keeping the Sabbath," &c. (Is 58:13, 14; Eze 20:12). A proof that the Sabbath, in the spirit of its obligation, was to be binding under the Gospel (Is 66:23). That gospel times are referred to is plain, from the blessing not being pronounced on the man who observed the sacrificial ritual of the Jewish law.

layeth hold--image from one grasping firmly some precious object which he is afraid of having forcibly snatched from him. The "Sabbath" here includes all the ordinances of divine worship under the new gospel law.

keepeth ... hand ... from ... evil--The observance of the second table of the law; as the "Sabbath" referred to the first table. Together, they form the whole duty of man, the worship of God and a holy life.