In some, especially "Western" authorities, Matthew 5:4, Matthew 5:5 are transposed (vide Westcott and Hort, 'Appendix'), possibly because the terms of Matthew 5:5 seemed to be more closely parallel to Matthew 5:3 (cf.
Meyer, Weiss), and also those of Matthew 5:4 fitted excellently with Matthew 5:6. But far the greater balance of evidence is in favour of the usual order, which also, though not on the surface, is in the deepest connexion with the preceding and the following verses.
They that mourn (cf. Isaiah 61:2). Our Lord does not define that which causes the mourning, but as the preceding and the following verses all refer to the religious or at least the ethical sphere, merely carnal and worldly mourning is excluded.
The mourning referred to must, therefore, be produced by religious or moral causes. Mourners for the state of Israel, so far as they mourned not for its political but for its spiritual condition (cf.
similar mourning in the Christian Church, 2 Corinthians 7:9,2 Corinthians 7:10), would be included (cf. Weiss, 'Life,' 2:142); but our Lord's primary thought must have been of mourning over one's personal state, not exactly, perhaps, over one's sins, but over the realized poverty in spirit just spoken of (cf.
Weiss-Meyer). As the deepest poverty lies in the sphere of the spirit, so the deepest mourning lies there also. All other mourning is but partial and slight compared with this (Proverbs 18:14). For they shall be comforted.
When? On having the kingdom of heaven (Matthew 5:3); i.e. during this life in measure (cf. Luke 2:25), but fully only hereafter. The mourning over one's personal poverty in spirit is removed in proportion as Christ is received and appropriated; but during this life such appropriation can be only partial.