In the Rigveda, the oldest of the Vedic texts, Mitra is mostly indistinguishable from Varuna, together with whom Mitra forms a dvandva pair Mitra-Varuna, and in which Mitra-Varuna has essentially the same characteristics as Varuna alone.
ɪnðə ɹˈɪɡvɛdə, ðɪ ˈoʊldɪst ʌvðə vˈɛdɪk tˈɛksts, mˈɪtɹə ɪz mˈoʊstli ˌɪndɪstˈɪŋɡwɪʃəbəl fɹʌm vɑːɹɹˈuːnə, təɡˌɛðɚ wɪð hˈuːm mˈɪtɹə fˈɔːɹmz ɐ dˈiːvˈændvə pˈɛɹ mˈɪtɹəvɑːɹɹˈuːnə, ænd ɪnwˌɪtʃ mˈɪtɹəvɑːɹɹˈuːnə hɐz ᵻsˈɛnʃəli ðə sˈeɪm kˌæɹɪktɚɹˈɪstɪks æz vɑːɹɹˈuːnə ɐlˈoʊn.