My husband does the prayer as required but he does not use any water after urinating, what is Islamic ruling…

Answer

It is necessary to use water, even if a few drops of water, after Istibra because ritual purity (Taharat) is obtained by use of water only. If a man does not use water, his prayers would be void. Albeit performing Istibra on its own is recommended (Mustahab) and not obligatory. For details about Istibra refer to the Islamic Laws book.