How can one show from the Bible that God is One?

That is not difficult. The Old Testament speaks of only one God from beginning to end, and whoever claims that the New Testament teaches otherwise must prove it.

No scripture describes the Oneness of God as perfectly and as beautifully as the short Surah Al-Ikhlas, whose opening is shown above. But that is a different question. Whether the Bible too teaches that God is One is easy to answer.

From beginning to end, the Old Testament speaks of no other God beside the one God. All the prophets of the Bible bear witness to Him alone. Not one of them even remotely mentions that there could be a second God or a partner in His Godhead.

From this follows an important principle. When something has always held true and someone claims that this time it is different, it is he who must prove it, not the one who stays with what is established. According to all the prophets of the Old Testament, belief in one God is the fixed rule. Whoever says that with the New Testament a Trinity suddenly appeared carries the burden of proof.

That burden is heavy. When a verse is quoted in support of the Trinity, it is worth reading a few verses before and after it. Usually the context itself gives the answer. That is why serious Christian scholars also say that the Bible speaks of one God. Only afterwards do they add that this one God is three in one.

And one question remains open. If there really were another God, why would God have revealed it so late, after all the earlier prophets had come and gone without saying a word about it?