The Lord Jesus early in the New Testament said, “Blessed are the pure in heart, for they shall see God” (Matt. 5:8). The New Testament concludes with New Jerusalem, “the city was pure gold” (Rev. 21:18) and in it we “will see His face” (22:4).
In ourselves we are not pure* in heart; we need the Lord’s cleansing*! And we can receive His cleansing! He cleansed our hearts in response to our faith and He cleanses us from unrighteousness when we confess our sins. These are two steps toward the purity of New Jerusalem.
We also need an experiential purification of our being. This requires our cooperation with the Lord.
First John 3:3 says, “everyone who has this hope [His second coming, v. 3:2] set on Him purifies himself, even as He is pure.” Here to purify ourselves is to abide in Christ by the teaching of the anointing (v. 2:27) and to live Him as our righteousness (v. 2:29).
Our cooperation with the Lord in purifying ourselves is also seen in 2 Timothy 2. “Let everyone who names the name of the Lord depart from unrighteousness” (v. 19b). “If therefore anyone cleanses himself from these [vessels of dishonor, v. 20], he will be a vessel unto honor, sanctified, useful to the master, prepared unto every good work” (v. 21). “Flee youthful lusts, and pursue righteousness, faith, love, peace with those who call on the Lord out of a pure heart” (v. 22).
We can turn from the unrighteous things, respond to the inner anointing, and pursue Christian virtures by calling on the Lord with companions. Thus the Lord will purify us, gradually making our inward nature and condition match the pure gold of New Jerusalem.
*For the verses cited in this post, clean and pure both come from the same New Testament Greek noun and cleanses and purifies both come from the related Greek verb.