S. R. Faruqi:

In the first line such a beautiful picture has been created that it beggars description. The picture is both visual (delicate wrists/forearms as white as silver) and active (having brought them into his hands, he released them). Then, the rhyme-word too is unexpected and meaningful. The meaning of ḳhayāl-e ḳhām is that the beloved's vows and promises were of two kinds: one, 'Let me go now, I'll meet you some other time'; and the other, she swore that in her heart was love for him. All these things are comprised in ḳhayāl-e ḳhām .

By contrast, Sauda uses thae same rhyme-word in an overt manner, so that the pleasure is less:

mihr-o-vafā-o-sharm-o-muruvvat sabhī kuchh us meñ samjhe the
kyā kyā dil dete vaqt us ko ham ne ḳhayāl-e ḳhām kiyā

[kindness and faithfulness, and shame and compassion-- we considered everything to be in her
how extensively, at the time of giving the heart, we formed a 'half-baked' opinion!]

Between 'silver' and 'half-baked' there's a wordplay, because raw [kachchī] silver is called sīm-e ḳhām .

Nasikh has used one aspect of this theme. The insha'iyah style has made the verse effective:

chhoṛ dete dast-e jānāñ kyūñ nah apne hāth se
zindagī bhar hāʾe malne the kaf-e ḥasrat hameñ

[why wouldn't we have released the beloved's hand from our hand?
for our whole life, alas, we had to 'wring the hand of longing']

FWP:

SETS == MUSHAIRAH; WORDPLAY
MOTIFS == VOWS
NAMES
TERMS

SRF finds the imagery in the first line-- the speaker takes her delicate silvery 'wrists' in his 'hands'-- to be extraordinarily beautiful. Then he also points out the wordplay between 'silvery' wrists and a 'half-baked' opinion, based on sīm-e ḳhām , a term for 'raw [kachchī] silver'.

This mushairah-verse wordplay with ḳhām , located as it is in the emphatic, closural, verse-final position, is clearly meant to form the chief pleasure of the verse. For it's also meaning-play. The lover formed about releasing her (raw-)silver wrists, a 'half-baked' or 'raw' opinion (see the definition above).

Compare Ghalib's G{81,7x}, in which similar wordplay is used, with just the same positioning.

SRF seems to feel that the ḳhayāl-e ḳhām refers to the beloved's unreliable promises; this is possible, but I think that because of bhūle , the case for its referring to the lover's foolish trust in her word is stronger.