Jamieson, Fausset and Brown on Philippians 4:15

15. Now--"Moreover." Arrange as Greek, "Ye also know (as well as I do myself)."

in the beginning of the gospel--dating from the Philippian Christian era; at the first preaching of the Gospel at Philippi.

when I departed from Macedonia--(Ac 17:14). The Philippians had followed Paul with their bounty when he left Macedonia and came to Corinth. 2Co 11:8, 9 thus accords with the passage here, the dates assigned to the donation in both Epistles agreeing; namely, "in the beginning of the Gospel" here, and there, at the time of his first visit to Corinth [Paley, Horæ Paulinæ]. However, the supply meant here is not that which he received at Corinth, but the supply sent to him when "in Thessalonica, once and again" (Php 4:16), [Alford].

as concerning giving and receiving--In the account between us, "the giving" was all on your part; "the receiving" all on mine.

ye only--We are not to wait for others in a good work, saying, "I will do so, when others do it." We must go forward, though alone.