Aaron’s rod is mentioned only in He 9:4, which locates the rod in the ark. An earlier tradition (Nu 17:10; cf. 1 K 8:9) preserves it ‘before’ the ark, on the spot on which it had budded (see HDB i. 3b). In either case the object was to secure a standing witness to the validity of the claims of the Aaronic priesthood (so Clement, 1 Cor. § 43). The rod has sometimes been identified as a branch of the almond tree; and both Jewish and Christian fancy has been busy with it. For early legends associating it symbolically with the cross, or literally with the transverse beam of the cross, see W. W. Seymour, The Cross in Tradition, History, Art, 1898, p. 83.
HDB Hastings’ Dict. of the Bible (5 vols.).