2 “Hitherto,” He says, “you have not asked anything in my name. Ask, and you shall receive, that your joy may be full.” This that He calls a full joy is certainly no carnal joy, but a spiritual one; and when it shall be so great as to be no longer capable of any additions to it, it will then doubtless be full. Whatever, then, is asked as belonging to the attainment of this joy, is to be asked in the name of Christ, if we understand the grace of God, and if we are truly in quest of a blessed life.
But if anything different from this is asked, there is nothing asked: not that the thing itself is nothing at all, but that in comparison with what is so great, anything else that is coveted is virtually nothing. For, of course, the man is not actually nothing, of whom the apostle says, “He who thinks himself to be something, when he is nothing.” But surely in comparison with the spiritual man, who knows that by the grace of God he is what he is, he who makes vain assumptions is nothing.
In this way, then, may the words also be rightly understood, “Verily, verily, I say unto you, if you shall ask anything of the Father in my name, He will give [it] you;” that by the words, “if anything,” should not be understood anything whatever, but anything that is not really nothing in connection with the life of blessedness. And what follows, “Hitherto you have not asked anything in my name,” may be understood in two ways: either, that you have not asked in my name, because a name that you have not known as it is yet to be known; or, you have not asked anything, since in comparison with that which you ought to have asked, what you have asked is to be accounted as nothing.
In order, then, that, they may ask in His name, not that which is nothing, but a full joy (since anything different from this that they ask is virtually nothing), He addresses to them the exhortation, “Ask, and you shall receive, that your joy may be full;” that is, ask this in my name, that your joy may be full, and you shall receive. For His saints, who persevere in asking such a good thing as this, will in no way be defrauded by the mercy of God.
Source: Tractates on the Gospel of John (New Advent)