Psalm 40

This is a complicated Psalm, with loads of important truths, but one thing stood out for me this morning.

The Psalm begins with David praising the LORD for hearing his prayer and rescuing him, and the hope that many others, seeing his own rescue, will come and put their trust in God, for in him is great blessing (1-5).
Verses 6-8 are hard to understand, though Hebrews 10 tells us that they're really speaking of the Christ, Jesus, and in 9&10, David remembers how he has told everyone of God's great deliverance - he hasn't concealed what God has done for him.

But it was vv11ff that made a big impression on me this morning:

11 As for you, O Lord, you will not restrain

your mercy from me;

your steadfast love and your faithfulness will

ever preserve me!

12 For evils have encompassed me

beyond number;

my iniquities have overtaken me,

and I cannot see;

they are more than the hairs of my head;

my heart fails me.

13 Be pleased, O Lord, to deliver me!

O Lord, make haste to help me!

14 Let those be put to shame and disappointed altogether

who seek to snatch away my life;

let those be turned back and brought to dishonor

who delight in my hurt!

15 Let those be appalled because of their shame

who say to me, “Aha, Aha!”

16 But may all who seek you

rejoice and be glad in you;

may those who love your salvation

say continually, “Great is the Lord!”

17 As for me, I am poor and needy,

but the Lord takes thought for me.

You are my help and my deliverer;

do not delay, O my God!

David says that even though he's surrounded by evil and his iniquities have overtaken him and they are more than the hairs of his head, yet the LORD will not restrain his mercy or his steadfast love & faithfulnes.
And when he concludes, 'As for me, I am poor and needy', King David can't mean that he hasn't got any money. Instead he's saying that he's poor and  needy spiritually - his prayer life and his loving obedience to God are lacking - and yet, 'the LORD takes thought for me.'
So, though I too often feel overwhelmed by my sinful actions & failures, the LORD God will not 'restrain' his mercy or love; God doesn't become stingy in his mercy & love even when I fail him. Why not? Because he is 'my helper and my deliverer'. And David prays that God would not delay in coming to complete his salvation because then he will be free from sin and failure.
And, significantly, in the middle of this section (12-15), there are again pointers to the Lord Jesus and his death (especially if, 'my iniquities' in v12 is understood to mean the iniquities that Jesus has taken upon himself on the cross). It's Jesus whom God rescued from his sneering enemies (15), and in rescuing Jesus, God rescues me.
'You are my helper and deliverer; do not delay, O my God.' (17)  'Come, Lord Jesus!' (Rev 22:20).