The book of Psalms is called by the Jews Sepher Tihillim, which more particularly signifies, the book of psalms, or hymns of praise. But there are two other names given by the Hebrews to the psalms, Zemer and Sher. The former is taken from, a root in Hebrew signifying to prune; and the latter from a word signifying power. And hence some have thought, that as the chief scope and tendency of the psalms is to lead to Christ, the former implies his humiliation, and the latter his glory. And it is remarkable, (but whether it may be considered as confirming this opinion I do not presume to say) that when the Lord Jesus was expounding to the two disciples, in his way to Emmaus, on the morning of his resurrection, the things concerning himself, he made use of those very arguments as proofs in his humiliation, and glory of his divine mission. "Ought not Christ (said he) to have suffered these things, and to enter into his glory." (Luke 24:26)
The Psalms have been generally divided into five heads, but it doth not appear that the Holy Ghost hath given any authority for this division. Taken as one grand whole, they form a complete epitome of the gospel; and from those which plainly point to Christ, and can refer to no other, we may venture to conclude that those which do not in our apprehension, the obscurity ariseth from our dulness, and not from any want of allusion to him. As to Jesus give all the prophets witness, and as the Psalms many of them are prophetical, evidently they are included. It is best in the perusal of every one of them to be on the look-out for Jesus, for precious are the things contained in the Psalms concerning him.
On those fifteen psalms entitled A song of degrees, from Psalms 120:1-7 to Psalms 134:1-3 included, I can offer no one observation to form the least conjecture what the title means. As the Holy Ghost hath not thought proper to explain the cause for which they are so called, it should seem to be the safest plan to avoid all unprofitable enquiries, than attempt to be wise above what is written. The Psalms themselves are full of Jesus, and therefore in the discovery and enjoyment of him it will be our highest wisdom to direct our researches, praying that as often as the Holy Ghost opens any part of this precious volume to our meditation, he that hath the key of David may open our heart to the right apprehension of them, to make us wise unto salvation, through the faith that is in Christ Jesus.