Reina-Valera Antigua Grammar

[JFellow]

Hello all. I am a new member, and user. I am perhaps just past beginner level in Spanish. I am working my way through a modified Michel Thomas Spanish course. I am also trying to read through the old 1569, 1602, and also 1602p Spanish Bible versions (also looking at others). I would like to read older Castilian Spanish as well as understand and speak Spanish fluently some day. Any grammar questions I find from reading the Reina Valera I try to research online, and usually I figure it out.

However in Genesis 2.3 I am stumped at something that may be simple.

Y bendijo Dios al día
séptimo, y santificólo,
porque en él reposó de toda
su obra que había Dios
creado y hecho.

And God blessed the
seventh day, and sanctified it:
because that in it he had
rested from all his work
which God created and made.

The only thing I am wondering about is , "porque en él reposó" specifically I am wondering if the "it" is "silently understood" somehow, even though it is not written. I would perhaps expect it to say, "porque en lo él reposó". Please, can anyone explain this? Thanks.