John 15:15

Henceforth I call you not servants
As they and the rest of the people of God had been, under the legal dispensation; for though they were children, yet differed nothing from servants; and were very much influenced and impressed with a servile spirit, a spirit of bondage unto fear, being kept under tutors and governors by a severe discipline; but now Christ being come in the flesh, and being about to lay down his life, and make reconciliation for them, henceforward he would not use, treat, or account them as servants:

for the servant knoweth not what his Lord doeth;
designs to do, or is about to do; he is not made privy to all his counsels and purposes; these are only opened to him as necessity requires; which was pretty much the case of the Old Testament church, who, comparatively speaking, were used as servants; and had not the knowledge of the mysteries of grace, and of the counsels of God, as they are now laid open under the Gospel dispensation:

but I have called you friends;
that is, accounted, reckoned of them, used them as his friends and familiar acquaintance; whom he told all his mind unto, and would go on to treat them as such; by leading them more and more, as they were able to bear it, into the designs of his grace, and the doctrines of his Gospel: just as Abraham was called the friend of God, and proved to be so, by his not concealing from him the thing he was about to do:

for all things I have heard of my Father, I have made known unto
you;
not all that he knew as the omniscient God, for there was no necessity that all such things should be made known to them; but all things which he had delivered to him as man and Mediator, by his Father, respecting the salvation of men; all things which he himself was to do and suffer, in order to obtain eternal redemption; and the whole of the Gospel, as to the essential and substantial parts of it, they were to preach; for otherwise, there were some things which as yet they were not able to bear, and were reserved to another time, to be made known unto them by his Spirit.