Typical of the importance that God’s Word attaches to the heart are the words found at Proverbs 4:23: “More than all else that is to be guarded, safeguard your heart, for out of it are the sources of life.”

Most fittingly, in his Sermon on the Mount Jesus stressed the need to keep the heart pure.

What will aid you to have a pure heart? The fear of displeasing Jehovah God, the fear of incurring his anger will aid you to do so. “The fear of Jehovah means the hating of bad.” “The fear of Jehovah is pure, standing forever.” No question about it, having a wholesome fear to displease Jehovah God will help you to have a pure heart.​—Prov. 8:13; Ps. 19:9.

Another aid to pureness of heart is a love of righteousness, a determination to have a good conscience. Nothing defiles a heart as much as a bad conscience, so acting in such a way as to have a good conscience will help you to keep your heart pure. The Bible shows that the apostle Paul was very concerned about having a good conscience.​—Acts 23:1; 24:16; 2 Cor. 1:12.

A warm, loving, grateful appreciation of all that Jehovah God has done for you will also help you to have a pure heart. Love of God will move you to keep his commandments, and these are not burdensome. Among those commandments is the one to safeguard, above all else, your heart.​—Prov. 4:23; 1 John 5:3.

Helpful to keeping your heart pure is also the hope of the reward of everlasting life, in the heavens or in an earthly paradise, that God holds out to all those who truly love and serve Him. “Everyone who has this hope set upon him purifies himself just as that one is pure.”​—1 John 3:3.

Fear to displease God, a good conscience, grateful appreciation and the hope of everlasting life​—how can you strengthen these? Jehovah God has provided three basic aids. One of these is his Word. Read it daily. Study it. (2 Tim. 3:16, 17) Another aid is God’s holy spirit, which aids you in understanding his Word and in strengthening your determination to have a pure heart. (Luke 11:13; 1 Cor. 2:9, 10) And God has also provided a visible organization, a “faithful and discreet slave” that provides spiritual food for you. It publishes Bible study aids and arranges for meetings where you can associate with fellow Christians who likewise are concerned with having pure hearts.​—Matt. 24:45-47; Heb. 10:23-25.