हर्फ़-ए-ना-गुफ़्ता = unsaid word
ला-फ़ानी = immortal
simple translation : let me write silence on the lips of 'sher' (verse) let me make immortal 'the unsaid word'.
Silence speaks more than words, if we can learn the art of reading silence, our heart will be filled with so many immortal words. Be it a word of love, a word of wisdom.