Jesus’ response to the disciples’ question is reminiscent of what he said in 17.20. In the earlier passage, however, the emphasis was upon the effective power of even a minimum faith, whereas here the emphasis is on the contrast between faith and doubt.
Truly, I say to you translates the same expression used in 6.2; most recently it was used in 18.13, 18, 19; 19.23, 28.
If you have faith is expressed by Good News Translation by a verb without an object: “if you believe….” In some languages it will be necessary to indicate the object of belief: “if you believe in God” or “… really believe in God.”
Doubt translates a verb used only one other time in Matthew. In 16.3 it appears in the active form with the meaning “interpret” or “discern.” Here the form is that of the aorist passive, which may mean “doubt,” “waiver,” “hesitate” (see Mark 11.23; Acts 10.20; Rom 4.20; 14.23; James 1.6; and Jude 22). In translation it may be necessary to indicate whom or what one doubts: “if you believe God and do not doubt what he can do” or “… and do not doubt his power.”
The expression what has been done to the fig tree is a passive form that may have to be translated with an active one. This will require a subject, so that translators may say “what I did to the fig tree.”
This mountain has been translated as “this hill” by many translations, for example, Good News Translation and Barclay. The use of this probably indicates that Jesus was pointing to some hill they were passing at the time. If it is natural in the receptor language to retain this, that should be done. Otherwise translators can say “this hill we see” or “this hill here.”
Be taken up and cast into the sea translates an aorist passive imperative. But a middle or reflexive form is more effective for English readers: “Get up and throw yourself” (Jerusalem Bible) and “Go, throw yourself” (New International Version). No particular sea is specified. It is best to be as general as possible in the translation too.
It will be done is translated “it will happen” by Phillips, Barclay, and Die Bibel im heutigen Deutsch. For some languages it may even be necessary to translate either “it will do what you said” or “it will throw itself into the sea.”
The rather long sentence of Revised Standard Version has been translated by two sentences in Good News Translation. Many translators find this model helpful.
Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .