Jamieson, Fausset and Brown on Acts 4:31-37

31-37. place was shaken--glorious token of the commotion which the Gospel was to make (Ac 17:6; compare Ac 16:26), and the overthrow of all opposing powers in which this was to issue.

they were all filled with the Holy Ghost, and spake, &c.--The Spirit rested upon the entire community, first, in the very way they had asked, so that they "spake the word with boldness" (Ac 4:29, 31); next, in melting down all selfishness, and absorbing even the feeling of individuality in an intense and glowing realization of Christian unity. The community of goods was but an outward expression of this, and natural in such circumstances.