Shiva Purana
चतुष्पादं सरस्वत्याः पारंगत्वं च शाश्वतम् ॥ न तुल्यं च सहस्रं तु पुत्राणां प्रददौ शिवः ॥ ६६॥
The four-legged Saraswati is eternally crossed. Lord Śiva gave him a thousand sons not equal to him.
english translation
catuSpAdaM sarasvatyAH pAraMgatvaM ca zAzvatam ॥ na tulyaM ca sahasraM tu putrANAM pradadau zivaH ॥ 66॥
hk transliteration by Sanscript