Final answer:
Muhammad's early teachings emphasized monotheism, social justice, and morality, which unified the Arabian Peninsula under Islam and laid the foundation for the religion's rapid expansion.
Step-by-step explanation:
The early teachings of Muhammad emphasized a monotheistic belief in Allah, which were radical in the context of the prevalent polytheistic practices in the Arabian Peninsula. His message, revealed to him by the angel Gabriel and later compiled into the Koran, also advocated for social justice and moral uprightness. Despite facing opposition from local leaders in Mecca, Muhammad's teachings had a profound impact, leading to the rapid expansion of Islam and its influence. His success in Medina and the eventual unifying of the Arab tribes under the banner of Islam demonstrated the transformative power of his message. By the time of his passing in 632 CE, Islam had grown considerably, leading to a new sense of identity and values within the Arab world.