Ch 5. verse 4: talks about Samkhya and Yoga branch of philosophy.
Ch 7. verse 13: talks about three Gunas (concept of Samkhya).
Ch 10. verse 26: mentions sage Kapila, one of the founders of Samkhya doctrine.
अश्वत्थः सर्ववृक्षाणां देवर्षीणां च नारदः।
गन्धर्वाणां चित्ररथः सिद्धानां कपिलो मुनिः।।10.26।।
Of all trees, I am the Pipal-tree; and of the divine seers, Narada; of the Gandharvas (the celestial musicians), Citraratha; of the perfected ones, the sage Kapila (the propounder of the Yoga system called Sankhya).
Ch 13. verse 5: this entire verse talks about the Samkhya concept.
This list is not exhaustive. There could be other verses as well.