But let patience have her perfect work

James 1:3
Knowing this,.... By experience; as everyone that is trained up in the school of affliction does: the apostle appeals to the saints, to whom he writes, for the truth of what he was about to say; and which he gives as a reason why they should rejoice in afflictions, because it is a known fact, 

 The trying of your faith works patience:

two things afflictions do when sanctified; one is, they try faith, the truth of it, and make it appear to be true, genuine, and precious, like gold tried in the fire; see 1Pe_1:6 and the other is, that they produce patience: saints being inured to afflictions, become by degrees more patient under them; whence it is good for a man to bear the yoke in his youth: this phrase may be understood, both of faith, which being tried by afflictions, produces patience; for where the one is in exercise, the other is also, and both are necessary under afflictive providences; and also of afflictions, which try faith, and being sanctified by the Spirit of God, work patience, which is a fruit of the Spirit; for otherwise the effect of them is impatience; and this agrees with the Apostle Paul in Rom_5:3.

 James 1:4
But let patience have her perfect work,.... 

Or effect; or be brought unto perfection; which may denote both the sincerity and continuance of it unto the end, with constancy: patience may be said to be perfect, when it appears to be real and sincere, and not dissembled; for as there may be a feigned faith, a dissembled love, and an hypocritical hope, so likewise a mere show of patience: and certain it is, that as there is a patience which is commendable, there is one that is not, 1Pe_2:20. 

And this phrase may also design the constant exercise of this grace to the end; for he that endures, or is patient, and continues so unto the end, shall be saved, and enjoy that perfection of glory and happiness expressed in the next clause: 

that ye may be perfect and entire, wanting nothing; which cannot be understood of the saints in this present life; only as they are in Christ, and in a comparative sense; or as perfection may denote sincerity, and uprightness; or of a perfection of parts, but not of degrees; for the saints are very imperfect in themselves, and are very far from being complete in soul,(mind power,will power, and emotions power) body, and spirit; and want many things, and are wanting in many things, both in the exercise of grace, and in the discharge of duty; but when patience has had its perfect work, and has been tried to the uttermost, and is found right, and has held out to the end; then shall the saints be perfect in holiness and happiness, and be entire, whole, and complete; as they will be in the resurrection morn, both in soul and body, and will want no good thing, and will be free from every sorrow, nor will they be deficient in any service; and to this sense agrees Jam_1:12.