Proverbs 3:21

3:21 My child, do not let them ¹  escape from your sight;

safeguard sound wisdom and discretion. ² 

Proverbs 4:21

4:21 Do not let them depart ³  from your sight,

guard ⁴  them within your heart; ⁵ 

[3:21]  ¹ tn The object of the verb “escape” is either (1) wisdom, knowledge, and understanding in vv. 13-20 or (2) “wisdom and discretion” in the second colon of this verse. Several English versions transpose the terms “wisdom and discretion” from the second colon into the first colon for the sake of clarity and smoothness (e.g., RSV, NRSV, NIV, TEV, CEV).
NIV takes the subject from the second colon and reverses the clauses to clarify that.

[3:21]  ² tn Or: “purpose,” “power of devising.”

[4:21]  ³ tn The Hiphil form יַלִּיזוּ (yallizu) follows the Aramaic with gemination. The verb means “to turn aside; to depart” (intransitive Hiphil or inner causative).

[4:21]  ⁴ tn Or “keep” (so KJV, NIV, NRSV and many others).

[4:21]  ⁵ sn The words “eyes” and “heart” are metonymies of subject representing the faculties of each. Cf. CEV “think about it all.”