Issue

The phrase ברב חסדך modifies the verb אבוא, but it is not clear exactly what the Psalmist is saying here.

Biblical Usage

Grammatical Parallels

In the Psalms, the verbal root בו"א takes the argument ב + abstract noun three other times:

Psa 69:28 תְּֽנָה־עָ֭וֹן עַל־עֲוֹנָ֑ם וְאַל־יָ֝בֹ֗אוּ בְּצִדְקָתֶֽךָ׃ ‘Add iniquity upon their iniquity; may they not come into Your righteousness.’
Psa 71:16 אָב֗וֹא בִּ֭גְבֻרוֹת אֲדֹנָ֣י יְהוִ֑ה 'I will come ? the strength of the Lord God.’
Psa 118:26 בָּר֣וּךְ הַ֭בָּא בְּשֵׁ֣ם יְהוָ֑ה בֵּ֝רַֽכְנוּכֶ֗ם מִבֵּ֥ית יְהוָֽה׃ ‘Blessed is the one who comes in/by the name of the Lord/’

In (1.) the bet is locative and is used metaphorically. God's צדקה is viewed as a container into which one enters. The point is that, presumably, they take on the quality of God's צדקה.

Secondary Literature

Weinfeld ^[1] points out that the structure of Psalm 5:3–8 is identical to the Psalms which enumerate the moral qualities of those entering the temple (Psalm 15; 24:3–6). In these lists, the positive qualities are stated only generally (e.g. פֹעֵל צֶדֶק ‘One who does what is right’ [Psa 15:2]) while the specifics take the form of negative statements (e.g., לֹֽא־רָגַ֨ל ׀ עַל־לְשֹׁנ֗וֹ ‘He does not slander with his tongue’ [Psa 15:3]). In the context of entering the temple, the most straightforward analysis is instrumental bet, viz., ‘Thanks to the abundance of Your ḥesed, I will enter Your house.’

רב חסד

Isa 63:7: here God's רב חסד is connected with His saving activities.
Joel 2:13: Here God insists that He is רב חסד in a plea for His people to turn back, presumabely a source of motivation for their repentance in light of the impending doom discussed in the previous verses.

References

↑ Weinfeld, Moshe. “הוראות למבקרי המקדש במקרא ובמצרים הקדומה [Instructions for Temple Visitors in Ancient Israel and in Ancient Egypt].” Tarbiz 62, no. 1 (1992): 5–15. Although note that the point of Weinfeld's article is to demonstrate the context (Sitz im Leben) of the entrance liturgies Psalm 15; 24:3–6; and Isaiah 33:14–16. On the basis of inscriptions with similar structure and content from Ptolmaic Egypt and Mesopotamia, Weinfeld argues that these Biblical texts could have been inscribed at the entrance of the temple.

[1] Weinfeld, Moshe. “הוראות למבקרי המקדש במקרא ובמצרים הקדומה [Instructions for Temple Visitors in Ancient Israel and in Ancient Egypt].” Tarbiz 62, no. 1 (1992): 5–15. Although note that the point of Weinfeld's article is to demonstrate the context (Sitz im Leben) of the entrance liturgies Psalm 15; 24:3–6; and Isaiah 33:14–16. On the basis of inscriptions with similar structure and content from Ptolmaic Egypt and Mesopotamia, Weinfeld argues that these Biblical texts could have been inscribed at the entrance of the temple.

[1]

Psam 5:8 ךתיב אובא ךדסח ברב