{Let not your heart be troubled} (m(8820)tarassesth(9320)hum(936e) h(880a)kardia). Not here the physical organ of life ( Lu 21:34 ), but
the seat of spiritual life (pneuma, psuch(885c)), the centre of
feeling and faith ( Ro 10:10 ), "the focus of the religious life"
(Vincent) as in  Mt 22:37 . See these words repeated in  14:27 .
Jesus knew what it was to have a "troubled" heart ( 11:33  13:31 ) where 	arass(935c) is used of him. Plainly the hearts of the
disciples were tossed like waves in the wind by the words of
Jesus in  13:38 . {Ye believe ... believe also} (pisteuete ...
kai pisteuete). So translated as present active indicative
plural second person and present active imperative of pisteu(935c).
The form is the same. Both may be indicative (ye believe ... and
ye believe), both may be imperative (believe ... and believe or
believe also), the first may be indicative (ye believe) and the
second imperative (believe also), the first may be imperative
(keep on believing) and the second indicative (and ye do believe,
this less likely). Probably both are imperatives ( Mr 11:22 ),
"keep on believing in God and in me."