And now I beseech thee, lady - Dr, “And now I entreat thee, Kyria,” (κυρία kuria.) See the introduction, Section 2. If this was her proper name, there is no impropriety in supposing that he would address her in this familiar style. John was probably then a very old man; the female to whom the Epistle was addressed was doubtless much younger.
Not as though I wrote a new commandment unto thee - John presumed that the command to love one another was understood as far as the gospel was known; and he might well presume it, for true Christianity never prevails anywhere without prompting to the observance of this law. See the notes at 1 Thessalonians 4:9.
But that which we had from the beginning - From the time when the gospel was first made known to us. See the notes at 1 John 2:7; 1 John 3:11.
That we love one another - That is, that there be among the disciples of Christ mutual love; or that in all circumstances and relations they should love one another, John 15:12, John 15:17. This general command, addressed to all the disciples of the Saviour, John doubtless means to say was as applicable to him and to the pious female to whom he wrote as to any others, and ought to be exercised by them toward all true Christians; and he exhorts her, as he did all Christians, to exercise it. It was a command upon which, in his old age, he loved to dwell; and he had little more to say to her than this, to exhort her to obey this injunction of the Saviour.