Is "Shu'ab al-Iman" (Branches of Faith) obligatory, and is one sinful for not doing them?

Faith comprises varying degrees, and it consists of sixty or seventy-odd branches; the highest of which is the saying, "There is no god but Allah," and the lowest is removing a harmful object from the path, and modesty is a branch of it. It is not necessary for all branches of faith to be obligatory, for the term "faith," when used unqualified, encompasses both the obligatory and the recommended acts of righteousness and good. Allah Almighty has indeed called prayer "faith," and it is the greatest of its physical characteristics. Faith is composed of a root without which it is incomplete, an obligation whose absence diminishes its possessor, and a recommended act whose omission diminishes one's high standing. The branches of faith are confined to the knowledge of Allah and His Messenger, and they are detailed in the Sharia, but the Lawgiver has not precisely specified their exact numbers for us; because the number of detailed acts of goodness exceeds the number mentioned in the Hadith, and the mention of seventy is for the purpose of indicating a large number, not for strict enumeration.