Commentary of Charles Spurgeon, Adam Clarke & Matthew Henry
And there went out a champion out of the camp of the 
Philistines, named Goliath, of Gath, whose height was six cubits and a span.
And he had an helmet of brass upon his head, and he was armed with a coat of mail; and the weight of the coat was five thousand shekels of brass. And he had greaves of brass upon his legs, and a target of brass between his shoulders. And the staff of his spear was like a weaver's beam; and his spear's head weighed six hundred shekels of iron: and one bearing a shield went before him.
Vs.4-7
There went out a champion — Our word champion comes from campus, the field.
Now concerning this champion observe --His prodigious size. He was of the sons of Anak, who at Gath kept their ground in Joshua's time (Joshua 11:22), and kept up a race of giants there, of which Goliath was one, and, it is probable, one of the largest.
Whose height was six cubits and a span — The word cubit signifies the length from cubitus, the elbow, to the top of the middle finger, which is generally rated at one foot six inches. ....it would then be nine feet nine inches, which is a tremendous height for a man.
The weight - five thousand shekels — Following Bishop Cumberland's tables, and rating the shekel at two hundred and nineteen grains, and the Roman ounce at four hundred and thirty-eight grains, we find that Goliath's coat of mail, weighing five thousand shekels, was exactly one hundred and fifty-six pounds four ounces avoirdupois. A vast weight for a coat of mail, but not all out of proportion to the man.
A target of brass between his shoulders — When not
actually engaged, soldiers threw their shields behind their back, so
that they appeared to rest or hang between the shoulders.
And one bearing a shield — הצנה hatstsinnah, from צן tsan, pointed or penetrating, if it do not mean some kind of a lance, must mean a shield, with what is called the umbo, a sharp protuberance, in the middle, with which they could as effectually annoy their enemies as defend themselves.
Goliath is called, in the Hebrew, not "champion", as we read it in the English, but the middle-man, the mediator.
There is the host of
the Philistines on the one side, and there is the host of Israel on the
other side.
A valley lies between them.....Now, it is exactly upon that ground
that the Lord Jesus Christ fought the battles of His people.
We fell
representatively in the first Adam, and our salvation now is by another
representative the second Adam.
He is the Middle-man, the "one Mediator
between God and men."
In His love to us we may view Him as stepping forward into the midst of the arena
which divides the camps of good and of evil, and there facing the defiant adversary. He stands to contend in our name
and on our behalf.
