Mine eyes fail for thy word,.... Either with looking for the Messiah, the essential Word, that was to be, and afterwards was made flesh, and dwelt among men; or for the fulfilment of the word of promise, on which he was made to hope; but that being deferred; and he believing in hope against hope, and looking out continually till it was accomplished, his eyes grew weary, and failed him, and he was just ready to give up all expectation of it; see Psa 77:8; saying, when wilt thou comfort me? The people of God are sometimes very disconsolate, and need comforting, through the prevalence of sin, the power of Satan's temptations, the hidings of God's face, and a variety of afflictions; when they apply to God for comfort, who only can comfort them, and who has his set times to do it; but they are apt to think it long, and inquire, as David here, when it will be.