If I am not downloading any content but just copying and using some text from a website for commercial use then would it be legal?
Example: Let's say I am copying and using some text for developing an application/service and selling it then would it be legal?
Are you in the US, Jacob? Copyright laws vary by country.
Whether you can take text from a website for a commercial use depends on many factors, including the specific website from which the text is taken and the type of text.
Example: You can take from a government website quotes from laws and the amount of text taken will not matter.
Corrections and clarifications to what was said earlier by ALawyer:
Federal registration of a copyright with the US Copyright Office has always been a condition necessary prior to filing a copyright infringement lawsuit. A "recent" court case did not make this so.
If a work is registered
before infringing activity or within three months of first publication of the work, the copyright holder is eligible for statutory damages of $750 to $30,000 per infringed work. If a work is registered afterwards, the copyright holder is limited to suing for the proven profits realized by the infringer and/or actual losses suffered by the copyright holder because of the infringement.
Attributing the copyrighted work to its author is not a defense to infringement.
And there is a statute of limitations for infringement (the time within which an infringement suit must be filed). It is 3 years (or when infringement should have been discovered) for civil suits and a criminal infringement suit must be filed within 5 years. A copyright holder cannot "sit on his rights" and allow damages to build.
More details would be nice - or, if you want to use someone else's words in a commercial manner, getting permission from the author in advance is the best way to avoid a lawsuit. Permission is generally granted in the form of a license.