Adam Clarke on Matthew 19:20

All these have I kept - I have made these precepts the rule of my life. There is a difference worthy of notice between this and our Lord's word. He says, Mat 19:17, τηρησον, keep, earnestly, diligently, as with watch and ward; probably referring not only to the letter but to the spirit. The young man modestly says, all these (εφυλαξα) have I observed; I have paid attention to, and endeavored to regulate my conduct by them. I have kept them in custody.

From my youth - Several MSS., versions, and fathers, leave out these words. Grotius and Mill approve of the omission, and Griesbach leaves them in the text with a note of suspicion. Perhaps the young man meant no more than that he had in general observed them, and considered them of continual obligation.

What lack I yet? - He felt a troubled conscience, and a mind unassured of the approbation of God; and he clearly perceived that something was wanting to make him truly happy.