And he could there do no mighty work, save that he laid his hands upon a few sick folk, and healed [them].
Note 2 at Mr 6:5: This verse says that Jesus could do (not would do) no mighty work, showing that He was hindered by "their unbelief" (Mt 13:58) in doing what He willed to do. Some degree of faith must be present in the person receiving the miracle in order for God to do the work (see note 2 at Lu 7:13, note 1 at Lu 8:45, and notes 1-2 at Lu 8:50-51).
It is God's will that no one should perish (Joh 3:16 with 2Pe 3:9), but many do because of unbelief. Likewise, it is God's will that we all be healed (3Jo 2 and see notes 1-2 at Mt 8:16-17), but not all are healed, because we fail to believe (Heb 4:2). It is a mistake to assume that whatever God wills will automatically come to pass. We play a part in receiving from God. If Jesus, who had no limitations, couldn't do all the mighty works He desired to do because of other people's unbelief, then most certainly we have to take into account the level of the peoples' faith that we minister to. This is the reason Jesus sought seclusion when performing certain miracles (see note 2 at Lu 8:51).
Compare this with De 7:17 where the Lord told the children of Israel that if they doubted in their hearts, He could not perform His promises to them (Nu 33:53) of dispossessing the nations in the Promised Land.