Dead Sea MSS: Nothing of Ps 41 has been preserved among the surviving Psalms MSS
This Psalm may be divided loosely into two parts. The first (vv. 2-5 [1-4]) is a prayer to YHWH with strong Wisdom features. It focuses on the righteous, and climaxes with a personal plea (by the Psalmist) for healing and deliverance. The second part (vv. 6-13 [5-12]) deals with the attacks by the wicked against the righteous, retaining the central theme-setting of the first part: the experience of illness by the righteous. As in several other Psalms we have studied thus far, the wicked respond with malice (slanderous taunts) to the suffering of the righteous. The prayer that concludes this second part (vv. 11-13 [10-12]) focuses on deliverance from these attacks by the wicked. A short verse of praise (v. 14 ) to YHWH brings the Psalm to a close.
Metrically, the Psalm tends to follow a 4+4 bicolon (couplet) format; however, there many irregularities as well, some of which may be evidence of textual corruption. Sadly, as noted above, there is no help available from the Dead Sea manuscripts, since Psalm 41 is not to be found among the surviving Psalms MSS.
The superscription gives the common direction, designating the work as another musical composition (romz+m!) “belonging to David”.
Verses 2-5 [1-4]
Verse 2 
“Happiness of (the one) giving consideration to (the) lowly <and needy>,
in (the) day of evil, YHWH will cause him to slip away [i.e. escape].”
There is a fundamental difficulty in the first line of this couplet. The meter of the couplet as it stands is 3+4, rather than the expected 4+4, suggesting that a word may have dropped out. Secondly, we have the word lD*: does it mean “lowly (one)” (from ll^D*), or “door” (from hl*D*)? The former is the more common lD* in the Psalms, where it is paired with the noun /oyb+a# (“needy, poor”), i.e., “the lowly and needy” (72:13; 82:3-4; 113:7). Many commentators thus would add here /oyb=a#w+, a reading which the LXX seems to assume. In this case, the first line would be:
“Happiness of (the one) giving consideration to (the) lowly <and needy>”
However, another possibility is raised by a comparison with Psalm 141:3, where we find the idea of keeping watch over “the door [lD*] of (one’s) lips” (i.e., guarding one’s speech).
Making the situation more difficult is the fact that the verb lk^c* only rarely takes a direct object or governs a prepositional phrase; such occurrences are even rarer when the verb form is a participle, such as the Hiphil form here /yk!c=m^, where it tends to be used as a substantive (“[one] giving consideration”, i.e., who is wise/prudent/understanding). The only such instances of the participle in the Psalms are 14:2 and 53:3 , while it is rather more common in the Proverbs. It is also in the Proverbs where we find the closest parallels to the usage here:
- Prov 16:20: “(the one) giving consideration upon a word” (rb*D*-lu^ lyK!c=m^)
- Prov 16:23: “(the) heart of a wise (man) gives consideration (to) his mouth, and upon his lips he continues receiving (instruction)”
- Prov 21:11: “in (his) giving consideration to (the) wise he receives knowledge”
- Prov 21:12: “(the) righteous (one) is giving consideration to (the) house of the wicked”
Prov 16:23 favors lD* as “door (of)” in Ps 41:2 , with an emended reading such as: “(the one) giving consideration to (the) door of <his lips >” (cf. Dahood, p. 249). On the other hand, Prov 21:11-13 favors an emended text that follows the LXX (cf. above), with the idea of paying attention to the lowly (lD*) and needy. The evidence, as I see it, is equally divided. It is unfortunate that nothing of Psalm 41 is preserved in the Dead Sea Psalms manuscripts; if verse 2  were present, it might well resolve the textual question.
Another factor is the beatitude context. This formulation (opening with yr@v=a^, “happiness of”, “how happy is…”) is frequently applied to the righteous, in terms of those who walk according to the path of YHWH, following the commands and precepts of the Torah, etc. As such, it seems that it might relate better to the idea of guarding one’s lips (and heart), as in Psalm 141:3-4. All things considered, I am inclined to adopt a reading that is comparable in meaning to Psalm 141:3:
“Happiness of (the one) giving consideration to (the) door of <his lips>”
“Happiness of (the one) giving consideration to (the) door of <his heart>”
However, with no textual support for such an emendation, it is probably safer, for the time being, to follow the LXX, in the manner indicated above.
Verse 3 
“YHWH shall guard him and keep him alive,
He shall make (him) happy in the land,
and shall not give him in(to the) throat of his enemies!”
Metrically, this verse is difficult and may possibly be corrupt; if so, there is, unfortunately, no reliable way to modify or emend the text. As it is stands, the verse reads as an irregular (3+2+3) tricolon. Conceptually, the lines are straightforward enough, following the promise of deliverance for the righteous in the second line of verse 2  (cf. above). The protection provided by YHWH, guarding the life of the righteous, relates to the idea of rescuing him “in the day of evil”.
The second line here is a bit awkward, and it may be preferable (along with Dahood, p. 249) to vocalize rvay as an active (Piel) form, rV@a^y+ (“he will make happy”), rather than the passive (Pual) of the MT, rV^a%y+ (“he will be made happy”). Clearly, the verb rv^a* relates to the beatitude formula the opens the Psalm (cf. above), and reflects the blessing that YHWH gives to the righteous. Those whom YHWH delivers in the time of evil, under his protection they will be safe and will prosper in the land (i.e., their life on earth).
In the final line, it is best to understand vp#n# in the concrete sense of “throat”, which is how the word is used occasionally in the Psalms (and other early poems). Another possible translation is “appetite”, which would conform more closely to the regular rendering of vp#n# as “soul” (cf. below). The enemies (lit. “hostile [one]s”) of the righteous seek to devour them, which can include the idea of causing their death. It is also possible that the wording here reflects the traditional image of Death personified as an all-consuming, ravenous entity, with a massive mouth/throat that seeks to swallow (devour) all things.
Verse 4 
“YHWH shall support him upon (the) couch of (his) sickness,
every place of his lying down shall you turn over in his illness.”
This couplet gives some confirmation that the “enemies” of verse 3  (as a collective or intensive plural) refer to death itself. We have encountered many Psalms where a life-threatening illness is involved, and that is clearly the focus here. The “day of evil” can take many forms, whereby the righteous are threatened and may be in danger of death; and, in the ancient world with its high rate of mortality, disease and illness frequently led to death. The promise here, continued from the opening verse, is that YHWH’s protection for the righteous will extend to help and healing in time of illness.
The shift from 3rd person to 2nd person may seem peculiar, but it is not at all uncommon in Near Eastern poetry. Here, we may view the shift as transitional to the Psalmist’s address to YHWH in verse 5 . The verb Ep^h* often means “overturn”, but here it is perhaps better to keep to the fundamental meaning of “turn”, in the sense of turning (i.e. changing) the “couch of sickness” into something else—namely, a place of health and wholeness. Every place where the righteous lies down, there will be healing and life, rather than sickness and the threat of death.
Verse 5 
“I said, ‘YHWH, show favor to me!
May you heal my soul,
for I have sinned against you!'”
This initial portion of the Psalm concludes with a plea to YHWH by the Psalmist. As is often the case, the Psalmist represents the righteous, and here the general Wisdom-sentiment of vv. 2-4 (i.e., instruction for the righteous) gives way to a personal appeal by a protagonist who personifies and embodies the righteous. Whether the author of the Psalm actually experienced such illness and suffering is beside the point; it is a topos that occurs repeatedly in the Psalms, and reflects an experience that would have been familiar to many faithful Israelites. As such, it relates to the common Wisdom-theme of the suffering of the righteous.
While illness could be viewed as an attack by a malevolent adversary, the monotheistic faith of the devout Israelite ultimately viewed YHWH Himself as the source of sickness and disease. Typically, it was thought as coming about as the result of sin—the disease being the punishment (by God) for such sin. Here the Psalmist admits that he has sinned against YHWH, recognizing that the illness that has struck him must be the result of his sin. It is a confession that is meant to demonstrate his faithfulness and devotion to YHWH, hoping (and expecting) that God will deliver him and remove the illness. He specifically prays that YHWH will heal (vb ap*r*) his soul (vp#n#, i.e., his life), but this concept of healing can have a deeper level of meaning as well, tied to the idea of repentance. In repenting of his sin, the Psalmist effectively asks that his life be made whole again, so that he can follow the path of God faithfully, avoiding any sinful ways that might turn him from the path.
References above marked “Dahood” are to Mitchell Dahood, S.J., Psalms I: 1-50, Anchor Bible [AB] vol. 16 (1965).