Salute Rufus; the same (it may be) of whom you may read, Mar_15:21.
Chosen in the Lord; a choice Christian, one eminent for gifts and graces. So, 2Jo_1:1, you read of an elect lady: he is supposed not to speak here of eternal election.
And his mother and mine; his mother by nature, mine by affection: she hath tendered me as a mother her son: see 1Ti_5:2.