मात्रास्पर्शास्तु कौन्तेय शीतोष्णसुखदुःखदाः। आगमापायिनोऽनित्यास्तांस्तितिक्षस्व भारत ॥

mātrā-sparśhās tu kaunteya śhītoṣhṇa-sukha-duḥkha-dāḥ āgamāpāyino ’nityās tans-titikṣhasva bhārata

The contacts of matter, O son of Kuntî, giving cold and heat, pleasure and pain, they come and go, impermanent; endure them bravely, O Bhârata.

In plain words: Krishna calls Arjuna "son of Kunti" (Kunti is Arjuna's mother). He says that when our senses meet the world, we feel cold and heat, pleasure and pain. These feelings come and go and do not last, so Arjuna should bear them bravely.