Charles H. Spurgeon on Psalms 86:11

Unite my heart to fear thy name. The end which he desired to secure was that he might truly fear God, or properly reverence and honour him; the means which he saw to be necessary for this was that his "heart" might be "united" in this one great object; that is, that his heart might be single in its views and purposes; that there might be no distracting purposes; that one great aim might be always before him. The word rendered unite —dxy, yahhad —occurs as a verb only in three places. In Ge 49:6 it is rendered united: "Unto their assembly, mine honour, be not thou united." In Isa 14:20 it is translated joined: "Thou shalt not be joined unto them." The adverb —dxy ya-hhad —occurs often, and is rendered together, Ge 13:6 22:6,8,19 36:7; et soepe. The idea is that of union, or conjunction; of being together; of constituting one; and this is accomplished in the heart when there is one great ruling object before the mind which nothing is allowed to interfere with. It may be added, that there is no more appropriate prayer which a man can offer than that his heart may have such unity of purpose, and that nothing may be allowed to interfere with that one supreme purpose. —Albert Barnes.