Blessed are the pure in heart, for they will see God.
Mathew Henry
This is the most comprehensive of all the beatitudes; here holiness and happiness are fully described and put together.
1. Here is the most comprehensive character of the blessed: they are pure in heart. Note, True religion consists in heart-purity. Those who are inwardly pure, show themselves to be under the power of pure and undefiled religion. ...
2. Here is the most comprehensive comfort of the blessed; They shall see God. Note
(1) It is the perfection of the soul's happiness to see God; seeing him, as we may by faith in our present state, is a heaven upon earth; and seeing him as we shall in the future state, in the heaven of heaven. ...
(2) The happiness of seeing God is promised to those, and those only, who are pure in heart. None but the pure are capable of seeing God, nor would it be a felicity to the impure. What pleasure could an unsanctified soul take in the vision of a holy God? ....
John Wesley
The Pure in Heart are those whose hearts have been purified through faith in the blood of Christ Jesus. They are purified from unholy affections and filthiness of the flesh and spirit by perfecting holiness in the fear of God (2 Cor 7:1). They have the spirit of gentleness and meekness and hunger and thirst after righteousness (verse 6).
The Pure in Heart shall see God. What a blessing this will be! God will bless them with the clearest communication of his Spirit as they proceed through this present life, the most intimate of fellowship with the Father and with His Son Jesus Christ (1 John 1:3). He will cause his glory and countenance to shine upon them. The Pure in Heart do see God dealing with every aspect of their lives, and they see his hand over them for good ....
The Pure in Heart shall see God. What a blessing this will be! God will bless them with the clearest communication of his Spirit as they proceed through this present life, the most intimate of fellowship with the Father and with His Son Jesus Christ (1 John 1:3). He will cause his glory and countenance to shine upon them. The Pure in Heart do see God dealing with every aspect of their lives, and they see his hand over them for good ....
Albert Barnes
Blessed are the pure in heart That is, whose minds, motives, and principles are pure; who seek not only to have the external actions correct, but who desire to be holy in heart, and who are so. Man looks on the outward appearance, but God looks on the heart.
They shall see God There is a sense in which all will see God, Rev 1:7 ... as a Judge, not as a Friend. In this place it is spoken of as a special favour. So also in Rev 22:4 And they shall see his face. To see the face of one, or to be in the presence of anyone, were terms among the Jews expressive of great favour. It was regarded as a high honour to be in the presence of kings and princes, and to be permitted to see them, Prov 22:29 He shall stand before kings. See also 2 Kings 25:19 Those that stood in the king’s presence; in the Hebrew, those that saw the face of the king; that is, who were his favourites and friends. So here, to see God, means to be his friends and favourites and to dwell with him in his kingdom.
A T Robertson
Shall see God (ton theon opsontai). Without holiness no man will see the Lord in heaven (Heb 12:14). The Beatific Vision is only possible here on earth to those with pure hearts. No other can see the King now. Sin befogs and beclouds the heart so that one cannot see God. Purity has here its widest sense and includes everything.