Arcana Coelestia #7446
7446. 'And tomorrow will this sign be' means the manifestation of Divine power thereby for evermore. This is clear from the meaning of 'tomorrow' as for evermore, dealt with in 3998; and from the meaning of 'a sign' as a corroboration of the truth, and consequent knowledge of it, dealt with in 6870, and therefore the manifestation of Divine power. For in former times truth, and at the same time Divine power were made manifest by means of signs.
Arcana Coelestia #6870
6870. 'And this will be the sign to you that I have sent you' means the recognition that the Divine would go forth from Him. This is clear from the meaning of 'the sign' as the corroboration of truth and consequent recognition that it is indeed so; and from the meaning of 'being sent' as going forth, dealt with in 2397, 4710, 6831, so that 'being sent by God' is going forth from the Divine. It is also the Divine going forth from Him, for one who comes forth from the Divine is receptive of the Divine and extends its influence further.