Are commas required?

Yoong Liat, you need the commas, because without them the meaning would be jumbled. If you want a rule, check out parenthetical expressions. Often these type expressions are set off by commas.

Thanks, Letty.

I would avoid the use of commas in that way, Yoong Liat. Personally I think that this is much better...

The book "The Old Man And The Sea" was written by Ernest Hemingway.

This is better still...

The novel "The Old Man And The Sea" was written by Ernest Hemingway.

Just calling it a "book" tells one nothing. Is it a collection of poems? A sailing guide? A biography? An autobiography?

This is best of all in my opinion:

The novel The Old Man And The Sea was written by Ernest Hemingway.

(If you are using a method of writing e.g. a word processor where italic text is possible)

Thanks, Contrex.

Note that there are various different conventions regarding the capitalisation of titles. One common convention is to capitalise every word, as I have done

The novel The Old Man And The Sea

Another one is to capitalise the first word and subsequent nouns and adjectives:

The novel The Old Man and the Sea

It is a matter of style preference.

Many thanks, Contrex.