Why should we know that Nehemiah at this point “prayed to the God of heaven”?

The term translated as prayed is by far the most common word used for prayer in the Old Testament. The term itself pictures God as the righteous Judge from whom the petitioner seeks adjudication. In the present context, this would link to Nehemiah’s prayer of Nehemiah 1:5–11, where he had asked God to restore his scattered people, such that he now asks God to judge between his own (God-centred) request and the king’s perhaps selfish and/or earthly agenda. The object of his prayer is the God of heaven, the same term Nehemiah had used in the introduction to his (habitual) prayer. This phrase highlights the majesty of God; recall the subsequent words in Nehemiah 1:5, great and awesome. This God, then, is both able to answer as well as worthy of such petition. We should further note that this phrase gives perspective to Nehemiah’s earlier words, Let the king live forever. Clearly, the king cannot do that simply because he is human and therefore mortal. But the God of heaven is eternal. The king may claim to have contact with the deities (and so access to unending longevity), but Nehemiah may go beyond a claim; he in fact actually has access to the Almighty.