What is the effect of a Marfu' Hadith on a jurisprudential ruling?

A Marfoo' Hadith is that which is attributed to the Prophet, peace and blessings be upon him, whether it is a saying, an action, an approval, or something similar to it. If its chain of narration is sound and free from defects, then it is obligatory to act upon it and it is valid to use it as evidence in jurisprudence and matters of creed.