Sirach 3:21
Ben Sira, Ecclesiasticus17 My child, perform your tasks with humility; then you will be loved by those whom God accepts. 18 The greater you are, the more you must humble yourself; so you will find favor in the sight of the Lord. 20 For great is the might of the Lord; but by the humble he is glorified. 21 Neither seek what is too difficult for you, nor investigate what is beyond your power. 22 Reflect upon what you have been commanded, for what is hidden is not your concern. 23 Do not meddle in matters that are beyond you, for more than you can understand has been shown you. 24 For their conceit has led many astray, and wrong opinion has impaired their judgment.
Genesis Rabbah 8:2
AggadahThen I [sc. the Torah] was by Him, as a nursling, and I was His delight day after day (Prov. VIII, 30); now the day of the Lord is a thousand years, as it is said, ‘For a thousand years in Thy sight are but as yesterday when it is past’ (Ps. XC, 4). That is the meaning of ‘Knowest thou this of old time?’ The Torah knows what was before the creation of the world, but you have no business to inquire about aught save ‘Since man was placed upon earth.’ R. Leazar said in Bar Sira’s name: About what is too great for thee inquire not; what is too hard for thee investigate not; about what is too wonderful for thee know not; of what is hidden from thee ask not; study what was permitted thee: thou hast no business with hidden things.
Notes and References
"... Source (1) is from Ben Sira 3:21–22. These lines appear in the name of R. Eleazar (a third-generation Palestinian Amora) in the Yerushalmi and in Bereshit Rabba. The tradition appears in a related context in the Babylonian Talmud in the name of an Amora known to cite Palestinian traditions (see above), and this source can therefore be considered secondary to the two Palestinian traditions, not an essentially Babylonian tradition. The closeness between all three of these rabbinic traditions and its two extant Hebrew versions in Ben Sira is striking. In fact, the second clause varies slightly both between the manuscripts of Ben Sira and between the rabbinic versions, but the rest of the text is almost identical in all five witnesses ..."
Labendz, Jenny R. The Book of Ben Sira in Rabbinic Literature (pp. 347-392) AJS Review, 30, 2006