(وَبِذَٰلِكَ أُمِرْتُ) (And this I have been commanded ): Allah (swt) commands that we devote all acts of worship and prayers purely and sincerely for His sake (swt) without being ostentatious, nor associating others with Him (swt), The One and The Only.
(وَأَنَا أَوَّلُ الْمُسْلِمِين) (and I am the first [among you] of the Muslims): Since the Message of Islam was revealed to Prophet Mohammad (saws), thus he is the first person to embrace Islam. In fact, Allah (swt) took the pledge from all the previous Prophets (PBUT) to believe in him (saws).