The journey to the Truth is not something that can be easily achieved without Divine assistance. There are too many pitfalls and multitudes of diversions. How can every individual – six billion in number – have direct access to God’s Presence and knowledge and still hold onto the precious rope of Oneness? What if a person confuses his own subjective desires with that of the universal Will?
This is where the dangers of multiplicity and the emergence of differences and separation are sure to begin if we don’t all have uniform laws and methods of understanding, which is why we need people who are authorised to receive and deliver the message of God and selflessly distribute it evenly, without bias or distortion.
So mankind has been blessed with chosen Guides and Messengers, sent by God to enlighten us and lead us on the path of truth and understanding. And the first message which every true Prophet and Messenger began with is the perfect call, to dismiss all concepts of false deities and gods and accept the existence of the One and Only Source of life and salvation – God, Who is without partners or peers.
We did not send any messenger before you except with the inspiration: ‘There is no god except Me; you shall [know and] worship Me ALONE.’ 
Therefore we find the names of the great teachers and advocates of the one path, united in their mission to convey the message of Oneness, such as Moses, Abraham, Jesus, David and enumerated in the Bible and Qur’an.
Look at some verses of the Divine code given to Moses, the Ten Commandments, and you will see one, two and three are solely concerned with that one single point.
Again, look at the clear message delivered by Jesus, Son of Mary, when asked what the greatest commandment is:
Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, this is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets. 
From this we understand the message of Monotheism (Tawhid) and the straight path which unites the roads of all truer teachers of the Truth. As we read in the very first chapter of the Qur’an revealed:
In the name of God, The Most Gracious, Most Merciful.
Praise be to Allah, the Cherisher and Sustainer of the universe;
Most Gracious, Most Merciful;
Master of the Day of Judgment.
You [alone] do we worship, and You [alone] we seek for help.
Guide us on the straight path;
The path of those on whom You have bestowed Your Grace,
those who do not deserve Your anger;
nor those who go astray.
Analysing the above verses, we come to the conclusion that all true messengers of God were unanimous in their emphasis on the need to serve only One Divine Being. And so all differences and conflicts between people of different races and religions could be greatly reduced if we returned to the original source of unity and knowledge and followed the road the Prophets carefully laid down – peace be upon them all.
4 The Qur’an, Al-Anbia (The Prophets) 21:25
5 Matthew 22:36-40