You probably knew this phrase was associated with Jesus and maybe that it was used in Revelation, but did you know that the Lord uses this same description of himself in the Old Testament? Employing a similar phrase to explain the actions of a king is used 9 times in the Chronicles. The image of first and last is used throughout the Bible for other reasons as well, like when Jesus says “the first shall be last” and he fulfilled this idea in a sense as well by being first (God) and becoming the least or last by dying a criminals death on the cross.
In Isaiah 41:4; 44:6; 48:12 the Lord proclaims to Israel that he is the first and he is the last. It is no accident that Jesus pulls this same moniker from the book of Isaiah and applies it to himself in Revelation to let his people know that he is the same God that Isaiah prophesied for. And of course the idea of him being first in the sense of being before all things and first in the since of being greatest are taught other places also.
Will you put your trust in and serve the one who was before the world existed and who will remain after all is said and done?