Psalms 38:20

They also that render evil for good - They whose characteristic it is to return evil for good, are opposed to me. This implies that those who were now seeking his ruin had been formerly benefitted by him. They were persons who cherished no grateful recollection of favors bestowed on them, but who found a pleasure in persecuting and wronging their benefactor. Compare Psalms 35:12. “Are my adversaries.” Are now opposed to me; have become my enemies.

Because I follow the thing that good is - This properly means, Because I follow the good. The Hebrew word rendered “because” - תחת tachath - means properly the lower part; what is underneath; then, below; beneath. The idea here is, that the “underlying reason” of what they did was that he followed good, or that he was a righteous man; or, as we say, This was “at the bottom” of all their dealings with him. Sinner as he felt he was (and as he acknowledged he was) before God, and true as it was that his “sickness” was brought upon him by God for his sinfulness, yet the reason why “men” treated him as they did, was that he was a friend of God - a religious man; and their conduct, therefore, was sheer persecution. We may, with entire consistency, be very humble before God, and acknowledge that we deserve all that He brings upon us; and yet, at the same time, we may be sensible that we have not wronged men, and that their conduct toward us is wholly undeserved, is most ungrateful, is sheer malignity against us.