How can a noble be both lord and vassal

Nobles can be both lord and vassal. Nobility was generally granted on feudal rights on a land. If a noble (noble 1) that have, for example, feudal rights on a big land (land A) gives feudal rights on a smaller part of this land (land A1) to another noble (noble 2), the latter becomes his vassal.

Explanation:

judaism, christianity and islam, are all abrahamic religions and therefore have in common the hebrew idea of a single god which is the source of all morality. the idea of the covenant is only related to judaism, while dharma is a concept of indian religions and the four noble truths are basic principles of buddhism.

the adoption by russian princes of the mongols' diplomatic rituals