Read Psalm 119:169-176.
The subjunctive is a grammatical mood in language that is all but forgotten in English (though it is alive and well in other languages.) Subjunctive forms of verbs are typically used to express various states of unreality such as wish, emotion, possibility, judgment, opinion, obligation, or action that has not yet occurred; the precise situations in which they are used vary from language to language. The only place we regularly find it still in English is in certain expressions using ‘may’ and ‘let’, many examples of which can be found in the concluding stanza of Psalm 119 (‘may my cry come before You… may my supplication come before You… may my lips overflow with praise… my Your laws sustain me… may my songs sing of Your word… may Your hand be ready to help me… let me live that I may praise You.’ Ps 119:169-175).
The psalmist expresses his desires and requests, but he is also aware that these things are beyond his own capability. He is not able to fulfil these requests; He needs God to do that.
Prayer is a dialogue between us and God. On our part, it involves our honesty, a pouring out of our thoughts, feelings, hopes and fears to God. Our part of prayer also involves both petition and supplication.
Petition is often a direct asking (using the imperative): ‘give me understanding according to Your Word’ (Ps 119:169); ‘deliver me according to Your promise’ (Ps 119:170); ‘seek Your servant’ (Ps 119:176). Supplication, more often than not, uses the subjunctive as we pray for God’s kingdom to come and God’s will to be done on earth as it is in heaven (Matt 6:10-11), as we earnestly plead with God to work His salvation out in our everyday lives.
Our part in prayer is only one part, for it is a dialogue, not a monologue. Petition and supplication are only part of our part in prayer, for there will be times when thankfulness, proclamation and adoration also have their place. But it is not surprising that the longest psalm in the Bible ends with a series of requests along with declarations (‘all Your commands are righteous’, ‘Your law is my delight’, ‘I have not forgotten Your commands’, ‘I have chosen Your precepts’ Ps 119:172-174, 176). Prayer cannot exist without a daily dependence on the God to whom we pray.