FWP:
SETS == EK; HUMOR
INDEPENDENCE: {9,1}
Khizr is, according to tradition, a guide to wanderers and the lost. So the speaker's saying that he doesn't need to follow him strikes a typically Ghalibian note of independence. But it's the second line that adds the wonderful touch of patronizing non-recognition. Not only does the speaker not need to follow Khizr as a valuable guide-- he doesn't even need to know who he is, and apparently doesn't know. (The commentators insist that the road is the mystical Sufi 'path', but nothing in the verse pushes us in that direction; Khizr traditionally guides lost travelers in a very literal sense.)
So when Khizr appears along the road, the speaker merely thinks, 'Oh, some [ik] elderly gentlemen has turned up, who's a fellow-traveler'. The phrasing makes it appear that the speaker is already on the road, already going in his own chosen direction, and Khizr just happens to turn up and join him. It's even possible that Khizr is following the speaker, rather than the other way around-- and that could equally well be why, as the first line points out, it's not necessary for the speaker to follow Khizr. On the complex possibilities of jaan'naa , see {16,5}.
Of course, that protean ik could also have many favorable implications. But even a 'unique' or 'excellent' fellow-traveler doesn't at all have to be a guide; those terms themselves can have a kind of jolly and amused (and thus patronizing) flavor of the kind that gives the verse its real relish.
The wordplay is also a treat: pai-ravii , jaanaa (which also, cleverly, means 'to go'), and ham-safar mesh together enjoyably.
Compare one of Mir's even more conspicuously patronizing looks at Khizr: M{1800,4}.
Nazm:
That is, our rank too, as a traveler on the Sufi path [martabah-e suluuk], is not a bit less than that of Khizr. (172)
== Nazm page 172