Here is an explanation from Su.Ki., a respected italki member. How often do you use the word "for" as a synonym to "because of"? Never. Well, not unless I'm quoting the Bible or 19th-century poetry, for example. Is it common in nowadays? No. It is not used in modern everyday English. or is it AN archaic form? Yes, it could be considered archaic. If you tried to use it in an essay, for example, your teacher would probably tell you to replace it with 'because'. https://www.italki.com/question/486074

Could you provide an example?

"For he" was more common than "because he" in English fiction until about 1930. Now "because he" is about 4X more common. Here is a Google Ngram. https://books.google.com/ngrams/graph?content=for+he%2Cbecause+he&year_start=1800&year_end=2000&corpus=16&smoothing=3&share=&direct_url=t1%3B%2Cfor%20he%3B%2Cc0%3B.t1%3B%2Cbecause%20he%3B%2Cc0