The reward is entering Paradise within the Ark of God. The reward comes after we die.
“Say: Is there any doubt concerning God? Behold how He hath come down from the heaven of His grace, girded with power and invested with sovereignty. Is there any doubt concerning His signs? Open ye your eyes, and consider His clear evidence. Paradise is on your right hand, and hath been brought nigh unto you, while Hell hath been made to blaze. Witness its devouring flame. Haste ye to enter into Paradise, as a token of Our mercy unto you, and drink ye from the hands of the All-Merciful the Wine that is life indeed.
Drink with healthy relish, O people of Bahá. Ye are indeed they with whom it shall be well. This is what they who have near access to God have attained. This is the flowing water ye were promised in the Qur’án, and later in the Bayán, as a recompense from your Lord, the God of Mercy. Blessed are they that quaff it.”
Gleanings From the Writings of Bahá’u’lláh, pp. 45-46
“Blessed art thou, O My name, inasmuch as thou hast entered Mine Ark, and art speeding, through the power of My sovereign and most exalted might, on the ocean of grandeur, and art numbered with My favored ones whose names the Finger of God hath inscribed. Thou hast quaffed the cup which is life indeed from the hands of this Youth, around Whom revolve the Manifestations of the All-Glorious, and the brightness of Whose presence they Who are the Day Springs of Mercy extol in the day time and in the night season.”
Gleanings, p. 302
Baha'u'llah has guaranteed it and that is good enough for me.