Magic Weapon

transmutation
level:1
Level Cleric 1, Paladin 1, Sorcerer/Wizard 1
Casting Time: 1 standard action
Components: V, S, DF
Range: touch
Target: weapon touched
Duration: 1 min./level
Saving Throw: Will negates (harmless, object); Spell Resistance yes (harmless, object)

Magic weapon gives a weapon a +1 enhancement bonus on attack and damage rolls. An enhancement bonus does not stack with a masterwork weapon's +1 bonus on attack rolls.

You can't cast this spell on a natural weapon, such as an unarmed strike (instead, see magic fang).

By the way…
This spell also affects siege engines and siege engine ammunition.