Daniel 10:12

set thine heart lit. give thine heart, i.e. apply thyself: a late idiom, found otherwise only in 1 Chronicles 22:19; 2 Chronicles 11:16; Ecclesiastes 1:13; Ecclesiastes 1:17; Ecclesiastes 7:21; Ecclesiastes 8:9; Ecclesiastes 8:16.

to understand viz. the future destiny of Israel. Anxious questionings on the future of his people were the occasion of his prolonged mourning and abstinence (Daniel 10:2).

and to humble thyself before thy God The verb, though it may be used more generally (Psalms 107:17), is applied here, as in Ezra 8:21 (-then I proclaimed a fast there, at the river Ahava, that we might humble ourselves before our God, to seek of him a straight way," &c.), to the self-denial and mortification accompanying a fast. The more common (and technical) expression in the same sense is to humble(or [R.V.] afflict) the soul: see Leviticus 16:29; Leviticus 16:31; Leviticus 23:27; Leviticus 23:29; Leviticus 23:32; Numbers 29:7 (all of the fast of the Day of Atonement); Isaiah 58:3; Isaiah 58:5; Psalms 35:13 (-I humbled my soul in fasting"); in a more general sense, Numbers 30:13 (of a vow of self-denial). The corresponding subst. ta-ănithhas the same meaning in Ezra 9:5 (R.V. marg.); and regularly in post-Biblical Hebrew (the Mishnic treatise -Ta-anith" deals with fasting).

and I am come because of thy words i.e. the prayer implied in Daniel 10:2. -I am come" is resumed at the beginning of Daniel 10:14, the explanation of the angel's delay in Daniel 10:13 being parenthetical.