Inserted in A.V. Better, the Lord and the Master as Rev. Both have the article.
Ought (ὀφείλετε)
The verb means to owe. It occurs several times in John's Epistles (1Jo 2:6; 1Jo 3:16; 1Jo 4:11; 3Jo 1:8). In the Gospel only here and Joh 19:7. Compare Luk 17:10. In Matthew's version of the Lord's prayer occur the two kindred words ὀφείλνμα, debt, and ὀφειλέτης, debtor. Jesus here puts the obligation to ministry as a debt under which His disciples are laid by His ministry to them. The word ought is the past tense of owe. Δεῖ, ought or must (see Joh 3:7, Joh 3:14, Joh 3:30, etc.) expresses an obligation in the nature of things; ὀφείλειν, a special, personal obligation.