Neither "benefactor" nor "shield" are good modern English translations for מָגֵן in Genesis 15:1. A better translation would be based on "defender" or "guardian". The reasons are that:
- the word מָגֵן is used here as a metaphor meaning defense or patronage1. The translation should follow the tenor of the metaphor rather than the vehicle
- "shield" is not used in English as a synonym for guardian, defender or patron as מגן is used in the MT
The word "benefactor" is close to "patron" (patron in the sense of protector) given as the second meaning of מָגֵן in the Even Shoshan concordance. It could be that the preacher had this in mind. Note that the NIV for this verse provides the alternate translation "sovereign". But neither "benefactor" nor "sovereign" sound consistently appropriate in the concordant verses (listed below). I think that they are both poor choices for translating מָגֵן in this verse.
Neither the ESV nor the OP's own translation deals with the possibility of translating מגן as a verb form of גנן rather than a noun, as Rashi and most other classical Jewish commentators read this verse. When translated as a verb form - and translating the tenses of both verbs correctly as present tense, the translation becomes both less labored and much closer to the sense of the Hebrew,
Fear not Avram, I am defending you. Your wages are very great.
The word מִגֵן, a pi'el verb form of the root מגנ meaning to hand over, turn in, deliver, or give as a gift, which is similar to the same Phoenician word, is found in three OT verses (ESV translation),
- Genesis 14:20
and blessed be God Most High, who has delivered your enemies into your hand!
- Hosea 11:8
How can I give you up, O Ephraim? How can I hand you over, O Israel? How can I make you like Admah? How can I treat you like Zeboiim? My heart recoils within me; my compassion grows warm and tender.
- Proverbs 4:9
She will place on your head a graceful garland; she will bestow on you a beautiful crown.
and once in the War of the Sons of Light Against the Sons of Darkness 18:12,
כיא אתה [...] לב גיבורים מגנתה לאין מעמד
Reading Genesis 15:1 as מִגֵן rather than מָגֵן creates a verse with a missing direct object - what it is that is handed over? However, if we read against the readers marks, specifically the zokef koton over לך that creates a clause break, then we can read the verse as does the Cambridge New English Bible,
"Do not be afraid, Abram, I am giving you a very great reward".
This reading requires two overrides of the MT and creates a thematic problem - how is the admonition not to be afraid connected with giving the great reward? As an aside, the word "reward" is not a straightforward translation for שכר, wages, as wages are the just compensation for work performed by covenant whereas a reward (in English) can be bestowed without respect to a covenant.
Avraham Even Shoshan's A New Concordance of the Bible gives two meanings for מגן in his concordance. The first meaning is "shield", a device used for defence , and the second meaning, by metaphor, is "protection", "defense" or "patronage" (מחסה).
The second meaning according to Even Shoshan is polysemic - related to, but different from the first. That is, the second meaning does not mean shield in the sense of a device used as a means of defense, but defense itself, the service that a shield provides, or patronage in the sense of someone who provides protection.
The verses in which מגן is used with this second meaning, "defence", defender" or "patron" are listed as follows, to which I have added the NIV translation:
- Genesis 15:1
Do not be afraid, Abram. I am your shield, your very great reward.
- II Samuel 22:31
As for God, his way is perfect: The Lord’s word is flawless; he shields all who take refuge in him.
- Psalms 3:3 [MT 4 ]
But you, Lord, are a shield around me, my glory, the One who lifts my head high.
- Psalms 18:30 [MT 31]
As for God, his way is perfect: The LORD's word is flawless; he shields all who take refuge in him.
- Proverbs 2:7
He holds success in store for the upright, he is a shield to those whose walk is blameless,
- Proverbs 30:5
Every word of God is flawless; he is a shield to those who take refuge in him.
- Psalms 84:11 [MT 12]
For the Lord God is a sun and shield; the Lord bestows favor and honor; no good thing does he withhold from those whose walk is blameless.
- Deuteronomy 33:29
Blessed are you, Israel! Who is like you, a people saved by the Lord? He is your shield and helper and your glorious sword. Your enemies will cower before you, and you will tread on their heights.
- II Samuel 22:36
You make your saving help my shield; your help has made me great.
- Psalms 18:35 [MT 36]
You make your saving help my shield, and your right hand sustains me; your help has made me great.
- II Samuel 22:3
my God is my rock, in whom I take refuge, my shield and the horn of my salvation. He is my stronghold, my refuge and my savior-- from violent people you save me.
- Psalms 18:2 [MT 3]
The LORD is my rock, my fortress and my deliverer; my God is my rock, in whom I take refuge, my shield and the horn of my salvation, my stronghold.
- Psalms 7:10 [MT 11]
My shield is God Most High, who saves the upright in heart.
- Psalms 144:2
He is my loving God and my fortress, my stronghold and my deliverer, my shield, in whom I take refuge, who subdues peoples under me.
- Psalms 28:7
The Lord is my strength and my shield; my heart trusts in him, and he helps me. My heart leaps for joy, and with my song I praise him.
- Psalms 119:114
You are my refuge and my shield; I have put my hope in your word.
- Psalms 59:11 [MT 12]
But do not kill them, Lord our shield, or my people will forget. In your might uproot them and bring them down.
- Psalms 84:11 [MT 10]
For the Lord God is a sun and shield: the Lord will give grace and glory: no good thing will he withhold from them that walk uprightly
- Psalms 89:18 [MT 19]
Indeed, our shield belongs to the LORD, our king to the Holy One of Israel.
- Psalms 33:20
We wait in hope for the Lord; he is our help and our shield.
- Psalms 115:9, 10,11
All you Israelites, trust in the Lord— he is their help and shield. House of Aaron, trust in the Lord— he is their help and shield. You who fear him, trust in the Lord— he is their help and shield.
- Job 41:15 [MT 7]
Its back has rows of shields tightly sealed together;
In Psalms 3:3 the use of "shield" might be the best word choice but in the other verse the use of "shield" as the English translation of מגו instead of "defender" or "protector" has the disadvantage of not providing a distinguishing translation for the distinct meaning of the word in Hebrew. That is, it is using one English word for at least two polysemic Hebrew words, besides giving the English reader a mistaken impression of what the text actually says. Having said that, using "shield" throughout is nowhere as confusing or as silly as using "the horn of my salvation" (II Samuel 22:3).