Skandapurana 16.35.109

16.35.109

nāpuṇyavadbhiḥ saṃprāptuṃ puṃbhiḥ śakyā mahānadī ..
prācī sarasvatī devi sarvatra ca sudurlabhā ..
viśeṣeṇa kurukṣetre prabhāse puṣkare tathā .. 109 ..

cannot be reached by men who lack merit. / The eastward-flowing Sarasvatī, O goddess, is exceedingly difficult to attain everywhere, / especially at Kurukṣetra, at Prabhāsa, and likewise at Puṣkara.”