Matthew 28:20

Teaching them to observe all things
All ordinances, not only baptism, but the Lord's supper; all positive institutions, and moral duties; all obligations, both to God and men; all relative duties that respect the world, or one another, those that are without, and those that are within; and these are to be taught them, and therefore to be insisted on in the ministry of the word; and not merely in order that they may know them, and have the theory of them, but that the may put them into practice:

whatsoever I have commanded you;
every thing that Christ has commanded, be it what it will, and nothing else; for Christ's ministers are not to teach for doctrines the commandments of men; or enjoin that on the churches, which is of their own, or other men's devising, and was never ordered by Christ; and for their encouragement he adds,

and lo! I am with you always, even unto the end of the world:
meaning, not merely to the end of their lives, which would be the end of the world to them; nor to the end of the Jewish world, or state, which was not a great way off, though this is sometimes the sense of this phrase; but to the end of the world to come, the Gospel church state, which now took place; or to the end of the present world, the universe: not that the apostles should live to the end of it; but that whereas Christ would have a church and people to the end of the world, and the Gospel and the ordinances of it should be administered so long, and there should be Gospel ministers till that time; Christ's sense is, that he would grant his presence to them, his immediate disciples, and to all that should succeed them in future generations, to the end of time: and which is to be understood not of his corporeal presence, which they should not have till then, but of his spiritual presence; and that he would be with them, in a spiritual sense, to assist them in their work, to comfort them under all discouragements, to supply them with his grace, and to protect them from all enemies, and preserve from all evils; which is a great encouragement both to administer the word and ordinances, and attend on them.