And when the sun was up,.... Some time, and its heat was increasing, and it began to shine out hot, and beat with some vehemency and strength; which may denote some sore temptation, or severe affliction, or fiery trial of persecution and tribulation; see Mt 13:21 for this is not to be understood of the glorious light of the Gospel, which, though very comfortable and refreshing, as well as illuminating to good men, is very distressing and tormenting to carnal minds; they cannot bear its truths and doctrines; this is the fire which comes out of the mouth of God's faithful witnesses, and torments them that dwell on the earth, and devours their enemies, Re 11:5.
And it, moreover, like the sun, has different effects on different objects; as the sun hardens clay, and melts wax, so the Gospel is to the hardening of some, and softening of others; to the one it is the savour of life unto life, and to the other the savour of death unto death; but this cannot be intended, because the word by these hearers is first received with joy.
Nor is Christ the sun of righteousness meant, who arises with healing in his wings, and gives grace and glory to his people; but the sun of persecution and affliction, in which sense the metaphor is used, in So 1:6 the heat of which the church patiently bore, though she was made black with it: but these hearers think it strange that such a fiery trial should befall them; wherefore, as they take up their profession in haste, they as quickly drop it; see Re 7:16.
They were scorched, and because they had not root, they withered away: they were offended with what they met with, for the sake of Christ, and the profession of his word; and therefore, not being rooted in him, nor in the love of God, nor having the root of the matter, true grace, in themselves, or, as Luke says, "lacked moisture", of divine grace, of the dews and waterings of it, fell away finally and totally.