Albert Barnes Commentary Psalms 42:3

"My tears have been my food day and night, While they continually say unto me, Where is thy God?" — Psalms 42:3 (ASV)

My tears have been my meat - The word translated 'tears' in this place is in the singular number and literally means weeping. . The word 'meat' here literally means bread and is used in the general meaning of food, as the word 'meat' is always used in the English version of the Bible. The English word 'meat,' which originally signified food, has gradually changed in its meaning until it now denotes in common usage animal food or flesh.

The idea here is that, instead of eating, he had wept. The state described is that which occurs so often when excessive sorrow takes away the appetite, or destroys the relish for food, and occasions fasting. This was the foundation of the whole idea of fasting: that sorrow, and especially sorrow for sin, takes away the desire for food for the time and leads to involuntary abstinence. Hence arose the related idea of abstaining from food to promote that deep sense of sin, or to produce a bodily condition favorable to a proper recollection of guilt.

Day and night - Constantly; without intermission. (See the notes at Psalms 1:2). “While they continually say unto me.” While it is constantly said to me; that is, by my enemies. .

Where is thy God? - (Psalms 22:8). The meaning here is, “He seems to be utterly forsaken or abandoned by God. He trusted in God. He professed to be his friend. He looked to him as his protector. But he is now forsaken, as if he had no God; and God is treating him as if he did not belong to him, as if he had no love for him, and no concern for his welfare.”