Definition
Latin. Literally, "oath of fealty." In old English law, the formal sworn oath by which a tenant or vassal bound himself in loyalty and obedience to his lord. The sacramentum fidelitatis was the legal instrument of the feudal bond: by swearing it, the tenant acknowledged the lord's superiority and undertook the obligations that tenure entailed. It was distinct from the more comprehensive oath of homage, which involved a ceremonial act of submission, though the two were closely connected in feudal practice.
The oath itself was understood to carry three essential components — truth, justice, and judgment — as reflected in the maxim recorded in Coke: "Sacramentum habet in se tres comites, veritatem, justitiam, et judicium; veritas habenda est in jurato; justitia et judicium in judice." That is, truth resided in the person swearing; justice and judgment resided in the judge or lord administering the oath.
Why It Matters in Research
This term appears almost exclusively in sources treating medieval and early modern English land law. Researchers encountering it in historical materials should recognize that it operates within a feudal framework largely dismantled in England by the Tenures Abolition Act 1660 and having no direct operational equivalent in modern common law jurisdictions.
The primary trap for corpus researchers is conflating sacramentum fidelitatis with the broader category of oaths generally. The term is technically specific: it refers to the feudal oath of loyalty owed by a tenant to a lord, not to judicial oaths, witness oaths, or oaths of allegiance owed to the Crown. A researcher working through plea rolls, register entries, or early treatises on tenure will find the term used precisely in that feudal-relational context.
The reference in both Black's and Burrill's to Reg. Orig. 303 — the Registrum Omnium Brevium, the register of original writs — signals that the sacramentum fidelitatis had procedural as well as substantive significance: it was the kind of oath whose breach or non-performance could have pleadable legal consequences.
Researchers in American colonial land history may encounter the term in materials dealing with manorial grants and quit-rent systems in early proprietary colonies, where feudal forms were sometimes nominally preserved. These instances are largely ceremonial survivals rather than operative legal obligations, but they appear in the documentary record and can mislead if read through a purely English feudal lens.
Historical Dictionary Support
Black's and Burrill's are in close agreement: both identify sacramentum fidelitatis as the oath of fealty in old English law and both cite Reg. Orig. 303 as the source for the form of the oath. Neither source attempts a detailed account of the oath's content or ceremony, treating it as a term requiring identification rather than extended explanation.
Black's adds the Coke maxim on the threefold nature of oaths (3 Inst. 160) and preserves a fragment of a second maxim — "Sacramentum si fatuum fuerit" — that the available text cuts off. That maxim, from the same portion of Coke's Institutes, addresses the legal effect of a foolish or ill-considered oath, a principle that the fuller text would connect to the broader law of oaths rather than to fealty specifically. Burrill's directs readers to the form of the oath as given in Law French in the Registrum, indicating awareness that the oath had a fixed verbal formula with jurisdictional and linguistic specificity.
What the historical dictionaries do not address: the distinction between fealty and homage, the gradations of the feudal oath across different tenures, or the question of what happened procedurally when fealty was withheld or forfeited. Researchers needing that doctrinal depth should consult Littleton's Tenures and Coke on Littleton directly.
Jurisdictional Note
The term has no operative significance in modern American or English law. It belongs to the law of feudal tenures abolished in England in the seventeenth century. In Scottish legal history, fealty oaths retained a somewhat different character under the distinct framework of Scots feudal tenure, which persisted formally until the Abolition of Feudal Tenure etc. (Scotland) Act 2000.