Tafsir of Al-Anbiya' 21:80

وعلمناه صنعة لبوس لكم لتحصنكم من بٲسكم

And We taught him the making of metal coats of mail, to protect you in your fighting. meaning, the manufacture of chain-armor. Qatadah said that before that, they used to wear plated armor; he was the first one to make rings of chain-armor. This is like the Ayah:

وألنا له الحديدأن اعمل سبغت وقدر فى السرد

And We made the iron soft for him. Saying: "Make you perfect coats of mail, and balance well the rings of chain armor.'' (34:10-11), meaning, do not make the pegs so loose that the rings (of chain mail) will shake, or make it so tight that they will not be able to move at all. Allah says:

لتحصنكم من بٲسكم

to protect you in your fighting. meaning, in your battles.

فهل أنتم شاكرون

Are you then grateful. means, `Allah blessed you when He inspired His servant Dawud and taught him that for your sake.' The Power of Suleiman is unparalleled And Allah tells: