John Gill Commentary 1 Samuel 16:6

"And it came to pass, when they were come, that he looked on Eliab, and said, Surely Jehovah`s anointed is before him." — 1 Samuel 16:6 (ASV)

And it came to pass, when they were come
Jesse and his sons, into the house where the entertainment was; and perhaps before they sat down, went into a private apartment by the direction of Samuel, where he acquainted Jesse with the business he came upon:

that he looked on Eliab ;
who was Jesse's firstborn, (1 Chronicles 2:13) , called Elihu, (1 Chronicles 27:18)

and said, surely the Lord's anointed is before him ;
or this is the person it is his pleasure should be anointed king.