The Sinai covenant refers to the agreement made through Moses between God and Israel; in return for their absolute commitment to God, Israel was to be God's chosen people
In the early centuries of the Church's existence, Church leaders considered the implications of biblical texts, their conviction that Jesus was uniquely the Son of God, and their experience of the power of the Holy Spirit guiding the lives of individual Christians and the life of the Church as a whole
There is one God in three Persons - Father, Son and Holy Spirit. Each Person possesses fully all the attributes of the Godhead - eternity, omnipotence, omniscience, etc.
It took the Church several centuries of debate to get its thinking clear on this and perhaps such texts represent early steps in that process of thought
1 Corinthians 8:6: 'yet for us there is but one God, the Father, from whom all things came and for whom we live, and there is but one Lord, Jesus Christ, through whom all things came and through whom we live'