Psalms 68:31

Princes shall come out of Egypt -That is, Shall come and acknowledge the true God. Egypt is referred to here as one of the most prominent of the foreign nations then known; and the idea is, that the distinguished men of foreign nations - the rulers and princes of the world - would come and submit themselves to God, and be united to his people. The word rendered “princes” here -חשׁמניםchashmaniym- occurs nowhere else in the Scriptures. It means, according to Gesenius (Lexicon), the fat; then, the rich; the opulent; nobles.