1. Defilement in the Old Testament:
Defilement in the Old Testament was physical, sexual, ethical, ceremonial, religious, the last four, especially, overlapping.
(1) Physical: "I have washed my feet; how shall I defile them?" (So 5:3).
(2) Sexual: which might be ceremonial or moral; of individuals by illicit intercourse (Le 18:20), or by intercourse at forbidden times (Le 15:24; 1Sa 21:5); of the land by adultery: "Shall not that land be greatly defiled?" (Jer 3:1 the American Standard Revised Version "polluted," usually substituted where the moral or religious predominates over the ceremonial).
(3) Ethical: "Your hands are defiled with blood" (Isa 59:3); "Neither shall they defile themselves any more with .... any of their transgressions" (Eze 37:23).
(4) Ceremonial: to render ceremonially unclean, i.e. disqualified for religious service or worship, and capable of communicating the disqualification.
(b) Holy objects were ceremonially defiled by the contact, entrance or approach of the defiled (Le 15:31; Nu 19:13); by the presence of dead bodies, or any remains of the dead (Eze 9:7; 2Ki 23:16: Josiah’s defilement of heathen altars by the ashes of the priests); by the entrance of foreigners (Ps 79:1; see Ac 21:28); by forbidden treatment, as the altar by being tooled (Ex 20:25); objects in general by contact with the unclean. Ceremonial defilement, strictly considered, implied, not sin, but ritual unfitness.
2. Defilement in New Testament:
The scope of defilement in its various degrees (direct, or primary, as from the person or thing defiled; indirect, or secondary, tertiary, or even further, by contact with the defiled) had been greatly widened by rabbinism into a complex and immensely burdensome system whose shadow falls over the whole New Testament life. Specific mentions are comparatively few. Physical defilement is not mentioned. Sexual defilement appears, in a figurative sense: "These are they that were not defiled with women" (Re 14:4). Ceremonial defilement is found in, but not approved by, the New Testament. Examples are: by eating with unwashed, "common," not ceremonially cleansed, hands (Mr 7:2); by eating unclean, "common," food (Ac 10:14; Peter’s vision); by intimate association with Gentiles, such as eating with them (not expressly forbidden in Mosaic law; Ac 11:3), or entering into their houses (Joh 18:28; the Pharisees refusing to enter the Pretorium); by the presence of Gentiles in the Temple (Ac 21:28).