Rashi: This is when I have strength to request my needs from You. When I do not have strength to pray, and the worry is stored in my heart, understand the thoughts of my heart (Shocher Tov 6).

Malbim: There are four conditions for a complete Tefilah, like Sefer ha'Ikarim says. (a) Eloquent expressions and concise statements - Amarai Ha'azinah. (b) The inner thought matches the external speech - Binah Hagigi. Also refer to 5:3:2:1, 5:3:4:2.

Rashi: It is a verb (understand); the accent is under the Beis. The same applies to "v'Im Binah Shim'ah Zos" (Iyov 34:16). This is like "Bin Tavin Es Asher Lefanecha" (Mishlei 23:1). Every other Binah in Tanach, the accent is under the Nun; it is a noun.

Radak: It is from Hagah (to think), just the middle letter of the root (Gimel) is doubled, just like "la'Chaziz Kolos" (Iyov 38:25), from the root Chazah.