Psalms 26:6-8

6. I will wash my hands in purity. Referring, in these words, to the ordinary use of the sacrifices, he makes a distinction between himself and those who professed to offer the same divine worship, and thrust themselves forward in the services of the sanctuary, as if they alone had the sole right to perform them. As David, therefore, and these hypocrites were one in this respect, that they entered the sanctuary, and surrounded the sacred altar together, he proceeds to show that he was a true worshipper, declaring, that he not only diligently attended to the external rites, but came to worship God with unfeigned devotion. It is obvious that he alludes to the solemn rite of washing which was practiced under the law. The washing of the hands in solemn protestation of innocence, on particular occasions, was enjoined by the Mosaic ritual, and was common among the Jews, Deuteronomy 21:6, 7. It was in common use among them before prayer; and the priests, in particular, were not to perform any sacred office in the sanctuary until they had poured water from the laver, which was set in the temple for that purpose, and washed their hands, Exodus 40:30-33.

Mudge conjectures that the expression, encompass, is probably taken from the custom of forming a ring round the altar at the time of worship. And Goodwyn informs us, that at the feast of tabernacles the people, on the seventh day, encompassed the altar seven times, carrying branches of palm trees in their hands in remembrance of the overthrow of Jericho, and singing hosannas. — Moses and Aaron, p. 132. David, however, may refer to the practice of the priests, who, when they offered sacrifices, went round about the altar; and his meaning may simply be, that as the priests first washed their hands, and then performed their sacred office at the altar; so he deeply felt the necessity of personal purity, in order to his engaging in the service of God.