Brihat Parashara Hora Shastra
भावे सूक्ष्मफलं ज्ञात्वा जातकस्य फलं वदेत् । केतौ स्वांशाद्द्वितीये वा तृतीये स्तब्धवाग् भवेत् ॥ ९३॥
Should Ketu be in the 2nd, or 3rd from Karakāńś, the native will be defective in speech, more so, if a malefic gives a Drishti to Ketu, as above.
english translation
bhAve sUkSmaphalaM jJAtvA jAtakasya phalaM vadet । ketau svAMzAddvitIye vA tRtIye stabdhavAg bhavet ॥ 93॥
hk transliteration by Sanscript