Tafsir of Al-Mu'minoon 23:52

وإن هذه أمتكم أمة واحدة

And verily, this your religion is one religion, means, `your religion, O Prophets, is one religion and one group, which is the call to worship Allah Alone with no partner or associate.' Allah said:

وأنا ربكم فاتقون

and I am your Lord, so have Taqwa. We have already discussed this in Surah Al-Anbiya'. The phrase

أمة واحدة

(one nation) is descriptive