the two noblest of things, which are sweetness and light
Note by H Craik to chapter 3 of Battle of the Books

Whatever the precise origin of this famous phrase (revived in our own day by Mr. Matthew Arnold), Swift has made it distinctively his own. It seems likely that the conjunction of qualities was taken from the advice to the pedant in Lucian's Lexiphanes

'Sacrifice chiefly to the Graces and to Perspicuity ,'— 'which ,' the adviser goes on, ' have now altogether forsaken you.' The phrase is cited in Boyle's Answer to Bentley's Dissertation (1698), which was chiefly written by Atterbury. But it is quite as likely that the citation was suggested by Swift (who may, like others, have contributed to the Answer) as that he borrowed it from thence. The passage in Lucian curiously illustrates Swift's attitude. The pedant is told not to imitate the latest fashions of the Sophists (Swift's Moderns ) but ' to follow with zeal the old models.'